java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
        at java.util.HashMap$KeyIterator.next(HashMap.java:828)
        at org.netbeans.api.visual.widget.Scene.validate(Scene.java:395)
        at org.netbeans.modules.uml.drawingarea.view.UMLNodeWidget.updateSize1(UMLNodeWidget.java:1187)
        at org.netbeans.modules.uml.drawingarea.view.UMLNodeWidget.access$000(UMLNodeWidget.java:111)
        at org.netbeans.modules.uml.drawingarea.view.UMLNodeWidget$1$1.run(UMLNodeWidget.java:1164)
        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:104)
        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)
Caused: java.lang.reflect.InvocationTargetException
        at java.awt.EventQueue.invokeAndWait(EventQueue.java:997)
        at javax.swing.SwingUtilities.invokeAndWait(SwingUtilities.java:1323)
        at org.netbeans.modules.uml.drawingarea.view.UMLNodeWidget$1.run(UMLNodeWidget.java:1162)