Exception in demo. Logout after session timeout

[uklance]

An unexpected application exception has occurred.
org.apache.tapestry5.ioc.internal.OperationException
trace
Triggering event 'logout' on ChatDemo
org.apache.tapestry5.runtime.ComponentEventException
context
eventType
logout
java.lang.NullPointerException
Filter stack frames Stack trace 
java.util.concurrent.ConcurrentHashMap.hash(Unknown Source)
java.util.concurrent.ConcurrentHashMap.remove(Unknown Source)
java.util.Collections$SetFromMap.remove(Unknown Source)
org.lazan.t5.atmosphere.demo.services.ChatManagerImpl.leaveRoom(ChatManagerImpl.java:60)
org.lazan.t5.atmosphere.demo.pages.ChatDemo.onLogout(ChatDemo.java:77)
org.lazan.t5.atmosphere.demo.pages.ChatDemo.advised$dispatchComponentEvent_64cece502c577a(ChatDemo.java)
org.lazan.t5.atmosphere.demo.pages.ChatDemo$Invocation_dispatchComponentEvent_64cece502c5779.proceedToAdvisedMethod(Unknown Source)
org.apache.tapestry5.internal.plastic.AbstractMethodInvocation.proceed(AbstractMethodInvocation.java:84)
org.apache.tapestry5.internal.services.ComponentInstantiatorSourceImpl$EventMethodAdvice.advise(ComponentInstantiatorSourceImpl.java:475)
org.apache.tapestry5.internal.plastic.AbstractMethodInvocation.proceed(AbstractMethodInvocation.java:86)
org.apache.tapestry5.internal.services.ComponentInstantiatorSourceImpl$EventMethodAdvice.advise(ComponentInstantiatorSourceImpl.java:475)
org.apache.tapestry5.internal.plastic.AbstractMethodInvocation.proceed(AbstractMethodInvocation.java:86)
org.lazan.t5.atmosphere.demo.pages.ChatDemo.dispatchComponentEvent(ChatDemo.java)
org.apache.tapestry5.internal.structure.ComponentPageElementImpl.dispatchEvent(ComponentPageElementImpl.java:932)
org.apache.tapestry5.internal.structure.ComponentPageElementImpl.processEventTriggering(ComponentPageElementImpl.java:1117)
org.apache.tapestry5.internal.structure.ComponentPageElementImpl.access$3100(ComponentPageElementImpl.java:61)
org.apache.tapestry5.internal.structure.ComponentPageElementImpl$5.invoke(ComponentPageElementImpl.java:1062)
org.apache.tapestry5.internal.structure.ComponentPageElementImpl$5.invoke(ComponentPageElementImpl.java:1059)
org.apache.tapestry5.internal.structure.ComponentPageElementResourcesImpl.invoke(ComponentPageElementResourcesImpl.java:146)
org.apache.tapestry5.internal.structure.ComponentPageElementImpl.triggerContextEvent(ComponentPageElementImpl.java:1058)
org.apache.tapestry5.internal.services.ComponentEventRequestHandlerImpl.handle(ComponentEventRequestHandlerImpl.java:81)
org.apache.tapestry5.internal.services.ImmediateActionRenderResponseFilter.handle(ImmediateActionRenderResponseFilter.java:42)
org.apache.tapestry5.internal.services.AjaxFilter.handle(AjaxFilter.java:42)
org.apache.tapestry5.services.TapestryModule$41.handle(TapestryModule.java:2476)
org.apache.tapestry5.internal.services.ComponentRequestHandlerTerminator.handleComponentEvent(ComponentRequestHandlerTerminator.java:43)
org.apache.tapestry5.services.InitializeActivePageName.handleComponentEvent(InitializeActivePageName.java:39)
org.lazan.t5.atmosphere.services.internal.PageGlobalsComponentRequestFilter.handleComponentEvent(PageGlobalsComponentRequestFilter.java:22)
org.apache.tapestry5.internal.services.ComponentEventDispatcher.dispatch(ComponentEventDispatcher.java:46)
org.apache.tapestry5.services.TapestryModule$RequestHandlerTerminator.service(TapestryModule.java:302)
org.apache.tapestry5.internal.services.RequestErrorFilter.service(RequestErrorFilter.java:26)
org.apache.tapestry5.services.TapestryModule$3.service(TapestryModule.java:902)
org.apache.tapestry5.services.TapestryModule$2.service(TapestryModule.java:892)
org.apache.tapestry5.internal.services.StaticFilesFilter.service(StaticFilesFilter.java:90)
org.apache.tapestry5.internal.services.CheckForUpdatesFilter$2.invoke(CheckForUpdatesFilter.java:105)
org.apache.tapestry5.internal.services.CheckForUpdatesFilter$2.invoke(CheckForUpdatesFilter.java:95)
org.apache.tapestry5.ioc.internal.util.ConcurrentBarrier.withRead(ConcurrentBarrier.java:85)
org.apache.tapestry5.internal.services.CheckForUpdatesFilter.service(CheckForUpdatesFilter.java:119)
org.apache.tapestry5.services.TapestryModule$HttpServletRequestHandlerTerminator.service(TapestryModule.java:253)
org.apache.tapestry5.internal.gzip.GZipFilter.service(GZipFilter.java:53)
org.apache.tapestry5.internal.services.IgnoredPathsFilter.service(IgnoredPathsFilter.java:62)
org.lazan.t5.atmosphere.services.internal.HttpServletHttpServletRequestFilter.service(HttpServletHttpServletRequestFilter.java:72)
org.lazan.t5.atmosphere.services.internal.AtmosphereHttpServletRequestFilter.service(AtmosphereHttpServletRequestFilter.java:50)
org.apache.tapestry5.services.TapestryModule$1.service(TapestryModule.java:852)
org.apache.tapestry5.TapestryFilter.doFilter(TapestryFilter.java:171)