java.lang.IllegalStateException: Problem in some module which uses Window System: Window System API is required to be called from AWT thread only, see http://core.netbeans.org/proposals/threading/
        at org.netbeans.core.windows.WindowManagerImpl.warnIfNotInEDT(WindowManagerImpl.java:1552)
        at org.netbeans.core.windows.WindowManagerImpl.topComponentID(WindowManagerImpl.java:1247)
        at org.openide.windows.WindowManager.findTopComponentID(WindowManager.java:525)
        at org.netbeans.core.windows.model.TopComponentSubModel.getID(TopComponentSubModel.java:365)
        at org.netbeans.core.windows.model.TopComponentSubModel.containsTopComponent(TopComponentSubModel.java:260)
        at org.netbeans.core.windows.model.DefaultModeModel.containsTopComponent(DefaultModeModel.java:260)
        at org.netbeans.core.windows.model.DefaultModel.containsModeTopComponent(DefaultModel.java:807)
        at org.netbeans.core.windows.Central.containsModeTopComponent(Central.java:1489)
        at org.netbeans.core.windows.ModeImpl.containsTopComponent(ModeImpl.java:384)
        at org.netbeans.core.windows.WindowManagerImpl.isEditorTopComponent(WindowManagerImpl.java:1273)
        at org.netbeans.core.windows.actions.CloseWindowAction.updateEnabled(CloseWindowAction.java:118)
        at org.netbeans.core.windows.actions.CloseWindowAction.<init>(CloseWindowAction.java:67)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(NativeConstructorAccessorImpl.java:0)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at java.lang.Class.newInstance0(Class.java:355)
        at java.lang.Class.newInstance(Class.java:308)
        at org.openide.loaders.InstanceSupport.instanceCreate(InstanceSupport.java:219)
        at org.openide.loaders.InstanceDataObject$Ser.instanceCreate(InstanceDataObject.java:1265)
        at org.openide.loaders.InstanceDataObject.instanceCreate(InstanceDataObject.java:749)
        at org.openide.loaders.FolderInstance.instanceForCookie(FolderInstance.java:572)
        at org.openide.loaders.FolderInstance$HoldInstance.instanceCreate(FolderInstance.java:1122)
        at org.openide.loaders.FolderInstance$1R.instances(FolderInstance.java:692)
        at org.openide.loaders.FolderInstance$1R.run(FolderInstance.java:713)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:573)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1005)