java.lang.reflect.UndeclaredThrowableException
        at $Proxy7.resultChanged(Unknown Source)
        at org.openide.util.lookup.AbstractLookup.notifyListeners(AbstractLookup.java:405)
        at org.openide.util.lookup.ProxyLookup$R.resultChanged(ProxyLookup.java:415)
        at org.openide.util.lookup.ProxyLookup.setLookups(ProxyLookup.java:109)
        at org.openide.explorer.DefaultEMLookup.updateLookups(DefaultEMLookup.java:96)
        at org.openide.explorer.DefaultEMLookup.propertyChange(DefaultEMLookup.java:131)
        at org.openide.util.WeakListenerImpl$PropertyChange.propertyChange(WeakListenerImpl.java:131)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:252)
        at org.openide.explorer.ExplorerManager$2.run(ExplorerManager.java:791)
        at org.openide.util.Mutex.doEvent(Mutex.java:1024)
        at org.openide.util.Mutex.readAccess(Mutex.java:239)
        at org.openide.explorer.ExplorerManager.fireInAWT(ExplorerManager.java:789)
        at org.openide.explorer.ExplorerManager.access$600(ExplorerManager.java:49)
        at org.openide.explorer.ExplorerManager$1AtomicSetSelectedNodes.updateSelection(ExplorerManager.java:208)
        at org.openide.explorer.ExplorerManager$1AtomicSetSelectedNodes.run(ExplorerManager.java:212)
        at org.openide.util.Mutex.readAccess(Mutex.java:246)
        at org.openide.explorer.ExplorerManager.setSelectedNodes(ExplorerManager.java:217)
        at org.openide.explorer.ExplorerManager$1SetExploredContextAndSelection.run(ExplorerManager.java:288)
        at org.openide.util.Mutex.readAccess(Mutex.java:246)
        at org.openide.explorer.ExplorerManager.setExploredContextAndSelection(ExplorerManager.java:305)
        at org.openide.explorer.view.BeanTreeView.selectionChanged(BeanTreeView.java:89)
        at org.openide.explorer.view.TreeView.callSelectionChanged(TreeView.java:654)
        at org.openide.explorer.view.TreeView$TreePropertyListener.run(TreeView.java:1010)
        at org.openide.util.Mutex.postRequest(Mutex.java:997)
        at org.openide.util.Mutex.postReadRequest(Mutex.java:421)
        at org.openide.explorer.view.TreeView$TreePropertyListener.valueChanged(TreeView.java:980)
        at javax.swing.tree.DefaultTreeSelectionModel.fireValueChanged(DefaultTreeSelectionModel.java:629)
        at javax.swing.tree.DefaultTreeSelectionModel.notifyPathChange(DefaultTreeSelectionModel.java:1076)
        at javax.swing.tree.DefaultTreeSelectionModel.setSelectionPaths(DefaultTreeSelectionModel.java:287)
        at javax.swing.JTree.setSelectionPaths(JTree.java:1181)
        at org.openide.explorer.view.TreeView$ExplorerTree$ModelHandler.treeStructureChanged(TreeView.java:1738)
        at javax.swing.tree.DefaultTreeModel.fireTreeStructureChanged(DefaultTreeModel.java:559)
        at javax.swing.tree.DefaultTreeModel.nodeStructureChanged(DefaultTreeModel.java:345)
        at org.openide.explorer.view.NodeTreeModel$Listener.reordered(NodeTreeModel.java:152)
        at org.openide.explorer.view.VisualizerChildren.reordered(VisualizerChildren.java:196)
        at org.openide.explorer.view.VisualizerEvent$Reordered.run(VisualizerEvent.java:160)
        at org.openide.util.Mutex.readAccess(Mutex.java:246)
        at org.openide.explorer.view.VisualizerNode$QP.run(VisualizerNode.java:583)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:454)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:141)
        at java.awt.Dialog$1.run(Dialog.java:540)
        at java.awt.Dialog.show(Dialog.java:561)
        at org.netbeans.core.windows.services.NbPresenter.superShow(NbPresenter.java:798)
        at org.netbeans.core.windows.services.NbPresenter.doShow(NbPresenter.java:841)
        at org.netbeans.core.windows.services.NbPresenter.run(NbPresenter.java:829)
        at org.openide.util.Mutex.doEventAccess(Mutex.java:1044)
        at org.openide.util.Mutex.readAccess(Mutex.java:170)
        at org.netbeans.core.windows.services.NbPresenter.show(NbPresenter.java:814)
        at java.awt.Component.show(Component.java:1133)
        at java.awt.Component.setVisible(Component.java:1088)
        at org.netbeans.core.windows.services.DialogDisplayerImpl$1AWTQuery.showDialog(DialogDisplayerImpl.java:154)
        at org.netbeans.core.windows.services.DialogDisplayerImpl.notify(DialogDisplayerImpl.java:169)
        at org.openide.text.CloneableEditorSupport.checkReload(CloneableEditorSupport.java:1661)
        at org.openide.text.CloneableEditorSupport.access$1600(CloneableEditorSupport.java:79)
        at org.openide.text.CloneableEditorSupport$11.run(CloneableEditorSupport.java:2036)
        at org.netbeans.editor.BaseDocument.runAtomicAsUser(BaseDocument.java:992)
        at org.netbeans.editor.GuardedDocument.runAtomic(GuardedDocument.java:217)
        at org.openide.text.NbDocument.runAtomic(NbDocument.java:341)
        at org.openide.text.CloneableEditorSupport$11.run(CloneableEditorSupport.java:2033)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:454)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
Caused by: java.lang.reflect.InvocationTargetException
        at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:324)
        at org.openide.util.WeakListenerImpl$ProxyListener.invoke(WeakListenerImpl.java:383)
        ... 69 more
Caused by: java.lang.AssertionError: Document was locked before starting the MDR transaction.
        at org.netbeans.modules.javacore.ExclusiveMutex.enter(ExclusiveMutex.java:118)
        at org.netbeans.mdr.NBMDRepositoryImpl.beginTrans(NBMDRepositoryImpl.java:227)
        at org.netbeans.modules.javacore.JMManager.getResource(JMManager.java:496)
        at org.netbeans.modules.javacore.JMManager.getResource(JMManager.java:488)
        at org.netbeans.modules.java.tools.OverrideAction.getElement(OverrideAction.java:147)
        at org.netbeans.modules.java.tools.OverrideAction.enable(OverrideAction.java:139)
        at org.openide.util.actions.NodeAction$DelegateAction.resultChanged(NodeAction.java:467)
        ... 73 more