java.util.ConcurrentModificationException
	at org.netbeans.modules.javacore.jmiimpl.javamodel.LightAttrList$LightAttrListIterator.testModCount(LightAttrList.java:372)
	at org.netbeans.modules.javacore.jmiimpl.javamodel.LightAttrList$LightAttrListIterator.hasNext(LightAttrList.java:423)
	at org.netbeans.modules.javanavigation.InheritanceTreeModel.loadContents(InheritanceTreeModel.java:161)
	at org.netbeans.modules.navigator.spi.TreeModelSupport$Roots.loadContents(TreeModelSupport.java:622)
	at org.netbeans.modules.navigator.spi.ListModelSupport$Loader.run(ListModelSupport.java:945)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
	at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:153)
	at java.awt.Dialog$1.run(Dialog.java:515)
	at java.awt.Dialog.show(Dialog.java:536)
	at org.netbeans.core.windows.services.NbPresenter.superShow(NbPresenter.java:800)
	at org.netbeans.core.windows.services.NbPresenter.doShow(NbPresenter.java:843)
	at org.netbeans.core.windows.services.NbPresenter.run(NbPresenter.java:831)
	at org.openide.util.Mutex.doEventAccess(Mutex.java:1146)
	at org.openide.util.Mutex.readAccess(Mutex.java:183)
	at org.netbeans.core.windows.services.NbPresenter.show(NbPresenter.java:816)
[catch] at org.netbeans.modules.javacore.UndoProgressListener$1.run(UndoProgressListener.java:63)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
	at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)