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.RecentViewList.fillList(RecentViewList.java:136)
   at org.netbeans.core.windows.RecentViewList.propertyChange(RecentViewList.java:124)
   at java.beans.PropertyChangeSupport.fire(PropertyChangeSupport.java:335)
   at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:327)
   at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:263)
   at org.netbeans.core.windows.RegistryImpl.doFirePropertyChange(RegistryImpl.java:329)
   at org.netbeans.core.windows.RegistryImpl.access$100(RegistryImpl.java:69)
   at org.netbeans.core.windows.RegistryImpl$1.run(RegistryImpl.java:170)
   at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
   at java.awt.EventQueue.access$400(EventQueue.java:97)
   at java.awt.EventQueue$3.run(EventQueue.java:697)
   at java.awt.EventQueue$3.run(EventQueue.java:691)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)