FreeMarker template error (HTML_DEBUG mode; use RETHROW in production!)

The following has evaluated to null or missing:
==> homePage  [in template "WEB-INF/site/views/widget/widget-guest-book.ftl" at line 5, column 6]

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Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
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FTL stack trace ("~" means nesting-related):
	- Failed at: #if homePage.editMode == true  [in template "WEB-INF/site/views/widget/widget-guest-book.ftl" at line 5, column 1]
	- Reached through: #include "/WEB-INF/site/views/widget/...  [in template "WEB-INF/site/pages/groups.ftl" at line 108, column 1]
----

Java stack trace (for programmers):
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freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
	at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
	at freemarker.core.UnexpectedTypeException.newDescriptionBuilder(UnexpectedTypeException.java:85)
	at freemarker.core.UnexpectedTypeException.<init>(UnexpectedTypeException.java:48)
	at freemarker.core.NonHashException.<init>(NonHashException.java:49)
	at freemarker.core.Dot._eval(Dot.java:57)
	at freemarker.core.Expression.eval(Expression.java:101)
	at freemarker.core.EvalUtil.compare(EvalUtil.java:114)
	at freemarker.core.ComparisonExpression.evalToBoolean(ComparisonExpression.java:78)
	at freemarker.core.ConditionalBlock.accept(ConditionalBlock.java:48)
	at freemarker.core.Environment.visit(Environment.java:344)
	at freemarker.core.Environment.visit(Environment.java:350)
	at freemarker.core.Environment.include(Environment.java:3139)
	at freemarker.core.Include.accept(Include.java:171)
	at freemarker.core.Environment.visit(Environment.java:344)
	at freemarker.core.Environment.visit(Environment.java:350)
	at freemarker.core.SwitchBlock.accept(SwitchBlock.java:79)
	at freemarker.core.Environment.visit(Environment.java:380)
	at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:291)
	at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
	at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
	at freemarker.core.Environment.visitIteratorBlock(Environment.java:654)
	at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
	at freemarker.core.Environment.visit(Environment.java:344)
	at freemarker.core.Environment.visit(Environment.java:350)
	at freemarker.core.Environment.process(Environment.java:323)
	at freemarker.template.Template.process(Template.java:383)
	at org.apache.struts2.views.freemarker.FreemarkerResult.doExecute(FreemarkerResult.java:182)
	at org.apache.struts2.result.StrutsResultSupport.execute(StrutsResultSupport.java:206)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:377)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:284)
	at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:260)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:179)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263)
	at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:49)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.FetchMetadataInterceptor.intercept(FetchMetadataInterceptor.java:78)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.CoopInterceptor.intercept(CoopInterceptor.java:57)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.CoepInterceptor.intercept(CoepInterceptor.java:55)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.doIntercept(ConversionErrorInterceptor.java:143)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.parameter.ParametersInterceptor.doIntercept(ParametersInterceptor.java:203)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.parameter.ParametersInterceptor.doIntercept(ParametersInterceptor.java:203)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:202)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:67)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:133)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:89)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.ActionFileUploadInterceptor.intercept(ActionFileUploadInterceptor.java:142)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:203)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:101)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:142)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:161)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:175)
	at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:99)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.csp.CspInterceptor.intercept(CspInterceptor.java:66)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:139)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.httpmethod.HttpMethodInterceptor.intercept(HttpMethodInterceptor.java:99)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:152)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:229)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:196)
	at com.opensymphony.xwork2.DefaultActionInvocation.executeConditional(DefaultActionInvocation.java:299)
	at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
	at org.apache.struts2.factory.StrutsActionProxy.execute(StrutsActionProxy.java:48)
	at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:723)
	at org.apache.struts2.dispatcher.ExecuteOperations.executeAction(ExecuteOperations.java:79)
	at org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter.handleRequest(StrutsPrepareAndExecuteFilter.java:152)
	at org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter.tryHandleRequest(StrutsPrepareAndExecuteFilter.java:135)
	at org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:123)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:176)
	at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:145)
	at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:92)
	at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:405)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:642)
	at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:408)
	at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:340)
	at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:277)
	at org.tuckey.web.filters.urlrewrite.NormalRewrittenUrl.doRewrite(NormalRewrittenUrl.java:233)
	at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:171)
	at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:145)
	at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:92)
	at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:405)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:174)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:166)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:400)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:894)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1741)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:840)