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.adjustSelectedTopComponent(TopComponentSubModel.java:296)
   at org.netbeans.core.windows.model.TopComponentSubModel.removeTopComponent(TopComponentSubModel.java:257)
   at org.netbeans.core.windows.model.DefaultModeModel.removeTopComponent(DefaultModeModel.java:140)
   at org.netbeans.core.windows.model.DefaultModel.removeModeTopComponent(DefaultModel.java:750)
   at org.netbeans.core.windows.Central.removeModeTopComponent(Central.java:987)
   at org.netbeans.core.windows.Central.userClosedTopComponent(Central.java:2037)
   at org.netbeans.core.windows.view.DefaultView.userClosedTopComponent(DefaultView.java:794)
   at org.netbeans.core.windows.view.ui.TabbedHandler.actionPerformed(TabbedHandler.java:337)
   at org.netbeans.core.multitabs.Controller.postActionEvent(Controller.java:133)
   at org.netbeans.core.multitabs.impl.CloseButtonHandler.mouseClicked(CloseButtonHandler.java:96)
   at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
   at java.awt.Component.processMouseEvent(Component.java:6528)
   at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
   at java.awt.Component.processEvent(Component.java:6290)
   at java.awt.Container.processEvent(Container.java:2234)
   at java.awt.Component.dispatchEventImpl(Component.java:4881)
   at java.awt.Container.dispatchEventImpl(Container.java:2292)
   at java.awt.Component.dispatchEvent(Component.java:4703)
   at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4898)
   at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4542)
   at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4462)
   at java.awt.Container.dispatchEventImpl(Container.java:2278)
   at java.awt.Window.dispatchEventImpl(Window.java:2739)
   at java.awt.Component.dispatchEvent(Component.java:4703)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
   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.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
   at java.awt.EventQueue$4.run(EventQueue.java:719)
   at java.awt.EventQueue$4.run(EventQueue.java:717)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
   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)