Dear Wicket Team,

I've got a silent NPE with the 1.5.7. with tomcat running under eclipse. It occurs only once, on the "first" page being accessed (in fact it is not really the first accessed page, because it does not occurs on every pages. But, when it  occurs, it is only one time but always for the same pages. At least for the exception bellow.

I also had a bigger stack trace which happens every time on every "impacted" pages. I unfortunately cannot give you the stack trace as I do not know how to repro (maybe multiple hot-deploy, I don't know). But I saw in the NPE that the exception came from the same line (at org.apache.wicket.pageStore.PageWindowManager.putWindowIndex(PageWindowManager.java:92)

It does not repro while using embedded jetty.

******************************************************************** *** WARNING: Wicket is running in DEVELOPMENT mode.              *** ***                               ^^^^^^^^^^^                    *** *** Do NOT deploy to your live server(s) without changing this.  *** *** See Application#getConfigurationType() for more information. *** ******************************************************************** May 29, 2012 8:38:02 PM org.apache.coyote.AbstractProtocol start INFO: Starting ProtocolHandler ["http-bio-8080"] May 29, 2012 8:38:02 PM org.apache.coyote.AbstractProtocol start INFO: Starting ProtocolHandler ["ajp-bio-8009"] May 29, 2012 8:38:02 PM org.apache.catalina.startup.Catalina start INFO: Server startup in 4853 ms INFO  - PropertiesFactory          - Loading properties files from file:/home/sebastien/Java/apache-tomcat-7.0.23/webapps/jquery-ui-samples/WEB-INF/classes/com/googlecode/wicket/jquery/ui/samples/SampleApplication.properties with loader org.apache.wicket.resource.IsoPropertiesFilePropertiesLoader@889ec59 Exception in thread "Wicket-PageSavingThread" java.lang.NullPointerException    at org.apache.wicket.pageStore.PageWindowManager.putWindowIndex(PageWindowManager.java:92)    at org.apache.wicket.pageStore.PageWindowManager.createPageWindow(PageWindowManager.java:396)    at org.apache.wicket.pageStore.DiskDataStore$SessionEntry.savePage(DiskDataStore.java:326)    at org.apache.wicket.pageStore.DiskDataStore.storeData(DiskDataStore.java:176)    at org.apache.wicket.pageStore.AsynchronousDataStore$PageSavingRunnable.run(AsynchronousDataStore.java:348)    at java.lang.Thread.run(Thread.java:679)

As usual, I do not exclude that I may have done something bad, but just in case...