NPE when using template builder

Steps to reproduce

• create new compound with 2 string fields
• update all content
• create new document
• add string

stacktrace:

30.11.2009 10:44:06 ERROR [org.apache.wicket.RequestCycle.logRuntimeException():1521]
java.lang.NullPointerException
at org.hippoecm.frontend.model.event.ObservableRegistry.removeObserver(ObservableRegistry.ja
va:138)
at org.hippoecm.frontend.model.event.ObservableRegistry$ObservationContext.unregisterObserve
r(ObservableRegistry.java:94)
at org.hippoecm.editor.tools.JcrTypeDescriptor.unsubscribe(JcrTypeDescriptor.java:423)
at org.hippoecm.editor.tools.JcrTypeDescriptor.processEvents(JcrTypeDescriptor.java:437)
at org.hippoecm.editor.tools.JcrTypeDescriptor.updateFields(JcrTypeDescriptor.java:469)
at org.hippoecm.editor.tools.JcrTypeDescriptor.attach(JcrTypeDescriptor.java:315)
at org.hippoecm.editor.tools.JcrTypeDescriptor.getFields(JcrTypeDescriptor.java:146)
at org.hippoecm.frontend.editor.builder.TemplateBuilder.updatePrototype(TemplateBuilder.java
:698)
at org.hippoecm.frontend.editor.builder.TemplateBuilder.access$800(TemplateBuilder.java:68)
at org.hippoecm.frontend.editor.builder.TemplateBuilder$BuilderTypeDescriptor.addField(Templ
ateBuilder.java:339)
at org.hippoecm.frontend.editor.builder.TemplateListPlugin$CategoryView$1.onClick(TemplateLi
stPlugin.java:161)
at org.apache.wicket.ajax.markup.html.AjaxLink$1.onEvent(AjaxLink.java:68)
at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:177)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.
java:299)
at org.apache.wicket.request.target.component.listener.BehaviorRequestTarget.processEvents(B
ehaviorRequestTarget.java:119)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycl
eProcessor.java:92)
at org.hippoecm.frontend.PluginRequestCycleProcessor.processEvents(PluginRequestCycleProcess
or.java:31)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1428)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:468)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:301)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)
at org.hippoecm.frontend.plugins.login.ConcurrentLoginFilter.doFilter(ConcurrentLoginFilter.
java:54)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:361)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:417)
at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:2
30)
at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:324)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:534)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:864)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:533)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:207)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:403)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:522)
30.11.2009 10:44:08 ERROR [org.apache.wicket.RequestCycle.logRuntimeException():1521]
java.lang.NullPointerException
at org.hippoecm.frontend.model.event.ObservableRegistry.removeObserver(ObservableRegistry.ja
va:138)
at org.hippoecm.frontend.model.event.ObservableRegistry$ObservationContext.unregisterObserve
r(ObservableRegistry.java:94)
at org.hippoecm.editor.tools.JcrTypeDescriptor.unsubscribe(JcrTypeDescriptor.java:423)
at org.hippoecm.editor.tools.JcrTypeDescriptor.processEvents(JcrTypeDescriptor.java:437)
at org.hippoecm.editor.tools.JcrTypeDescriptor.updateFields(JcrTypeDescriptor.java:469)
at org.hippoecm.editor.tools.JcrTypeDescriptor.attach(JcrTypeDescriptor.java:315)
at org.hippoecm.editor.tools.JcrTypeDescriptor.getFields(JcrTypeDescriptor.java:146)
at org.hippoecm.frontend.editor.builder.TemplateBuilder$BuilderTypeDescriptor.getFields(Temp
lateBuilder.java:351)
at org.hippoecm.frontend.editor.builder.TemplateBuilder$BuilderTypeDescriptor.addField(Templ
ateBuilder.java:324)
at org.hippoecm.frontend.editor.builder.TemplateListPlugin$CategoryView$1.onClick(TemplateLi
stPlugin.java:161)
at org.apache.wicket.ajax.markup.html.AjaxLink$1.onEvent(AjaxLink.java:68)
at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:177)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.
java:299)
at org.apache.wicket.request.target.component.listener.BehaviorRequestTarget.processEvents(B
ehaviorRequestTarget.java:119)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycl
eProcessor.java:92)
at org.hippoecm.frontend.PluginRequestCycleProcessor.processEvents(PluginRequestCycleProcess
or.java:31)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1428)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:468)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:301)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)
at org.hippoecm.frontend.plugins.login.ConcurrentLoginFilter.doFilter(ConcurrentLoginFilter.
java:54)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:361)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:417)
at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:2
30)
at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:324)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:534)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:864)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:533)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:207)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:403)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:522)