NullPointerExceptions in tree while working in the console

09.06.2011 11:27:25 ERROR [org.apache.wicket.RequestCycle.logRuntimeException():1529] Exception in rendering component: [MarkupContainer [Component id = indent]]
org.apache.wicket.WicketRuntimeException: Exception in rendering component: [MarkupContainer [Component id = indent]]
at org.apache.wicket.Component.renderComponent(Component.java:2729)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1539)
at org.apache.wicket.Component.render(Component.java:2521)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1441)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1604)
at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1528)
at org.apache.wicket.Component.renderComponent(Component.java:2690)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1539)
at org.apache.wicket.markup.html.tree.AbstractTree$TreeItem.onRender(AbstractTree.java:227)
at org.apache.wicket.Component.render(Component.java:2521)
at org.apache.wicket.Component.renderComponent(Component.java:2631)
at org.apache.wicket.ajax.AjaxRequestTarget.respondComponent(AjaxRequestTarget.java:901)
at org.apache.wicket.ajax.AjaxRequestTarget.respondComponents(AjaxRequestTarget.java:681)
at org.apache.wicket.ajax.AjaxRequestTarget.respond(AjaxRequestTarget.java:591)
at org.apache.wicket.request.AbstractRequestCycleProcessor.respond(AbstractRequestCycleProcessor.java:105)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1258)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1436)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:486)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:319)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:370)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.hippoecm.frontend.ResourceRewriteFilter.doFilter(ResourceRewriteFilter.java:129)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.hippoecm.frontend.plugins.login.ConcurrentLoginFilter.doFilter(ConcurrentLoginFilter.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:396)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at org.apache.wicket.extensions.markup.html.tree.DefaultAbstractTree.isNodeLast(DefaultAbstractTree.java:609)
at org.apache.wicket.extensions.markup.html.tree.DefaultAbstractTree.access$000(DefaultAbstractTree.java:50)
at org.apache.wicket.extensions.markup.html.tree.DefaultAbstractTree$1.onComponentTagBody(DefaultAbstractTree.java:301)
at org.apache.wicket.Component.renderComponent(Component.java:2690)
... 43 more