clicking around in cms sometimes results in NPEs (after proper error message in dialog?)

for example typically a stacktrace you get below. Normally, it happens after some prior 'correct' error message: for example, I am user X, and I am not allowed to change some value into another value. Then, I get an error in a dialog saying: Access Denied. Changing the value to a correct one again, result in stacktrace below

java.lang.NullPointerException at org.hippoecm.frontend.model.properties.JcrPropertyValueModel.load(JcrPropertyValueModel.java:221) at org.hippoecm.frontend.model.properties.JcrPropertyValueModel.getObject(JcrPropertyValueModel.java:113) at org.apache.wicket.Component.getModelObject(Component.java:1559) at org.apache.wicket.Component$3.compare(Component.java:511) at org.apache.wicket.Component.setModelObject(Component.java:2888) at org.apache.wicket.markup.html.form.FormComponent.updateModel(FormComponent.java:1069) at org.apache.wicket.ajax.form.AjaxFormComponentUpdatingBehavior.onEvent(AjaxFormComponentUpdatingBehavior.java:138) at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:163) at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:293) at org.apache.wicket.request.target.component.listener.BehaviorRequestTarget.processEvents(BehaviorRequestTarget.java:100) at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:91) at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1171) at org.apache.wicket.RequestCycle.step(RequestCycle.java:1248) at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1349) at org.apache.wicket.RequestCycle.request(RequestCycle.java:493) at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:387) at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:199) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1065) at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:246) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1065) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:365) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:185) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:689) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:391) at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:146) at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:139) at org.mortbay.jetty.Server.handle(Server.java:285) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:457) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:765) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:628) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:203) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:357) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:329) at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:475)