FreeMarker template error:The following has evaluated to null or missing:==> title [in template 'WEB-INF/t/cms/com.ggzy.www/com.ggzy.www/content/jyxx.html' at line *, column **]Tip: If the failing expression is known to be legally null/missing, either specify a default value with 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 parenthessis: (myOptionVar.foo)!myDefault, (myOptionVar.foo)??The failing instruction (FTL stack trace):----------==> ${title} [in template 'WEB-INF/t/cms/com.ggzy.www/com.ggzy.www/content/jyxx.html' at line *, column **]----------Java stack trace (for programmers):----------freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:**)at freemarker.core.EvalUtil.coerceModelToString(EvalUtil.java:***)at freemarker.core.Expression.evalAndCoerceToString(Expression.java:***)at freemarker.core.DollarVariable.accept(DollarVariable.java:**)at freemarker.core.Environment.visit(Environment.java:***)at freemarker.core.MixedContent.accept(MixedContent.java:**)at freemarker.core.Environment.visit(Environment.java:***)at freemarker.core.Environment.process(Environment.java:***)at freemarker.template.Template.process(Template.java:***)at com.jeecms.common.web.springmvc.SimpleFreeMarkerView.renderMergedTemplateModel(SimpleFreeMarkerView.java:***)at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:***)at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:***)at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:****)at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:***)at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:***)at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:***)at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:***)at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:***)at javax.servlet.http.HttpServlet.service(HttpServlet.java:***)at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:***)at javax.servlet.http.HttpServlet.service(HttpServlet.java:***)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:***)at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:**)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:***)at com.jeecms.common.web.XssFilter.doFilter(XssFilter.java:**)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:***)at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:***)at org.apache.shiro.web.servlet.AbstractShiroFilter$*.call(AbstractShiroFilter.java:***)at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:**)at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:**)at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:***)at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:***)at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:***)at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:***)at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:***)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:***)at com.jeecms.common.web.InterviewFilter.doFilter(InterviewFilter.java:**)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:***)at org.springframework.orm.hibernate*.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:***)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:***)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:***)at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:**)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:***)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:***)at com.jeecms.common.web.ProcessTimeFilter.doFilter(ProcessTimeFilter.java:**)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:***)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:***)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:***)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:***)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:***)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:***)at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:****)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:***)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:***)at org.apache.coyote.http**.AbstractHttp**Processor.process(AbstractHttp**Processor.java:****)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:***)at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:***)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:****)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:***)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:**)at java.lang.Thread.run(Thread.java:***)