java.lang.NullPointerException: preferredID attribute not specified for null
   at org.netbeans.core.spi.multiview.MultiViewFactory$MapMVD.get(MultiViewFactory.java:390)
   at org.netbeans.core.spi.multiview.MultiViewFactory$MapMVD.preferredID(MultiViewFactory.java:427)
   at org.netbeans.core.multiview.MultiViewPeer.preferredID(MultiViewPeer.java:602)
   at org.netbeans.core.multiview.MultiViewCloneableTopComponent.preferredID(MultiViewCloneableTopComponent.java:208)
   at org.openide.windows.WindowManager.findTopComponentID(WindowManager.java:551)
   at org.netbeans.core.windows.model.TopComponentSubModel.getID(TopComponentSubModel.java:382)
   at org.netbeans.core.windows.model.TopComponentSubModel.getOpenedTopComponentsIDs(TopComponentSubModel.java:347)
   at org.netbeans.core.windows.model.DefaultModeModel.getOpenedTopComponentsIDs(DefaultModeModel.java:393)
   at org.netbeans.core.windows.model.DefaultModel.getModeOpenedTopComponentsIDs(DefaultModel.java:966)
   at org.netbeans.core.windows.Central.getModeOpenedTopComponentsIDs(Central.java:922)
   at org.netbeans.core.windows.ModeImpl.getOpenedTopComponentsIDs(ModeImpl.java:386)
   at org.netbeans.core.windows.WindowManagerImpl.findModeForOpenedID(WindowManagerImpl.java:980)
   at org.netbeans.core.windows.actions.CloseAllButThisAction.obtainTC(CloseAllButThisAction.java:168)
   at org.netbeans.core.windows.actions.CloseAllButThisAction.run(CloseAllButThisAction.java:146)
   at org.openide.util.Mutex.doEvent(Mutex.java:1356)
   at org.openide.util.Mutex.readAccess(Mutex.java:355)
   at org.netbeans.core.windows.actions.CloseAllButThisAction.updateEnabled(CloseAllButThisAction.java:141)
   at org.netbeans.core.windows.actions.CloseAllButThisAction.access$000(CloseAllButThisAction.java:68)
   at org.netbeans.core.windows.actions.CloseAllButThisAction$1.actionPerformed(CloseAllButThisAction.java:91)
   at javax.swing.Timer.fireActionPerformed(Timer.java:312)
   at javax.swing.Timer$DoPostEvent.run(Timer.java:244)
   at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:312)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:745)
   at java.awt.EventQueue.access$300(EventQueue.java:103)
   at java.awt.EventQueue$3.run(EventQueue.java:706)
   at java.awt.EventQueue$3.run(EventQueue.java:704)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:715)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)