FreeMarker template error!


Expression content is undefined on line 2, column 10 in WEB-INF/ftl/layouts/components/header.ftl.
The problematic instruction:
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==> if-else  [on line 2, column 5 in WEB-INF/ftl/layouts/components/header.ftl]
 in include "/WEB-INF/ftl/layouts/components/header.ftl" [on line 25, column 14 in WEB-INF/ftl/layouts/decorators/store.ftl]
----------

Java backtrace for programmers:
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freemarker.core.InvalidReferenceException: Expression content is undefined on line 2, column 10 in WEB-INF/ftl/layouts/components/header.ftl.
	at freemarker.core.TemplateObject.assertNonNull(TemplateObject.java:124)
	at freemarker.core.TemplateObject.invalidTypeException(TemplateObject.java:134)
	at freemarker.core.Dot._getAsTemplateModel(Dot.java:78)
	at freemarker.core.Expression.getAsTemplateModel(Expression.java:89)
	at freemarker.core.BuiltIn$existsBI._getAsTemplateModel(BuiltIn.java:636)
	at freemarker.core.BuiltIn$existsBI.isTrue(BuiltIn.java:647)
	at freemarker.core.IfBlock.accept(IfBlock.java:80)
	at freemarker.core.Environment.visit(Environment.java:196)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:196)
	at freemarker.core.Environment.include(Environment.java:1375)
	at freemarker.core.Include.accept(Include.java:155)
	at freemarker.core.Environment.visit(Environment.java:196)
	at freemarker.core.MixedContent.accept(MixedContent.java:92)
	at freemarker.core.Environment.visit(Environment.java:196)
	at freemarker.core.Environment.process(Environment.java:176)
	at freemarker.template.Template.process(Template.java:232)
	at com.opensymphony.webwork.sitemesh.FreeMarkerPageFilter.applyDecorator(FreeMarkerPageFilter.java:127)
	at com.opensymphony.webwork.sitemesh.TemplatePageFilter.applyDecorator(TemplatePageFilter.java:86)
	at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:59)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
	at com.opensymphony.webwork.dispatcher.ActionContextCleanUp.doFilter(ActionContextCleanUp.java:88)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
	at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:200)
	at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:283)
	at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:773)
	at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:703)
	at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:895)
	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
	at java.lang.Thread.run(Thread.java:595)