java.lang.AssertionError
   at org.netbeans.modules.uml.drawingarea.UMLDiagramTopComponent.<init>(UMLDiagramTopComponent.java:261)
   at org.netbeans.modules.uml.drawingarea.UMLDiagramManager.showDiagram(UMLDiagramManager.java:514)
   at org.netbeans.modules.uml.drawingarea.UMLDiagramManager.openDiagram(UMLDiagramManager.java:138)
   at org.netbeans.modules.uml.drawingarea.dataobject.UMLDiagramEditorSupport.openDiagramEditor(UMLDiagramEditorSupport.java:91)
   at org.netbeans.modules.uml.drawingarea.dataobject.UMLDiagramDataObject$OpenViewEdit.open(UMLDiagramDataObject.java:158)
   at org.netbeans.modules.uml.drawingarea.dataobject.UMLDiagramDataObject$OpenViewEdit.edit(UMLDiagramDataObject.java:170)
   at org.netbeans.modules.project.ui.ProjectUtilities$1.open(ProjectUtilities.java:115)
   at org.netbeans.modules.project.ui.ProjectUtilities.openProjectFiles(ProjectUtilities.java:523)
   at org.netbeans.modules.project.ui.OpenProjectList$9.run(OpenProjectList.java:1183)
   at org.netbeans.modules.project.ui.OpenProjectList$9.run(OpenProjectList.java:1180)
   at org.openide.util.Mutex$1AWTWorker.run(Mutex.java:1377)
   at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:199)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:137)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:178)
   at java.awt.Dialog$1.run(Dialog.java:1046)
   at java.awt.Dialog$3.run(Dialog.java:1098)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.awt.Dialog.show(Dialog.java:1096)
   at java.awt.Component.show(Component.java:1563)
   at java.awt.Component.setVisible(Component.java:1515)
   at java.awt.Window.setVisible(Window.java:842)
   at java.awt.Dialog.setVisible(Dialog.java:986)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.lang.AssertionError
   at org.openide.util.RequestProcessor.post(RequestProcessor.java:422)
   at org.netbeans.modules.project.ui.OpenProjectList.open(OpenProjectList.java:587)
   at org.netbeans.modules.project.ui.actions.OpenProject.actionPerformed(OpenProject.java:142)
   at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
   at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
   at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
   at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
   at javax.swing.AbstractButton.doClick(AbstractButton.java:357)
   at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1223)
   at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:1264)
   at java.awt.Component.processMouseEvent(Component.java:6267)
   at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
   at java.awt.Component.processEvent(Component.java:6032)
   at java.awt.Container.processEvent(Container.java:2041)
   at java.awt.Component.dispatchEventImpl(Component.java:4630)
   at java.awt.Container.dispatchEventImpl(Container.java:2099)
   at java.awt.Component.dispatchEvent(Component.java:4460)
   at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4577)
   at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4238)
   at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4168)
   at java.awt.Container.dispatchEventImpl(Container.java:2085)
   at java.awt.Window.dispatchEventImpl(Window.java:2478)
   at java.awt.Component.dispatchEvent(Component.java:4460)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:137)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)