java.lang.NullPointerException
   at org.netbeans.modules.uml.diagrams.edges.AssociationLabelManager.getLabelText(AssociationLabelManager.java:434)
   at org.netbeans.modules.uml.diagrams.edges.AssociationLabelManager.createLabel(AssociationLabelManager.java:212)
   at org.netbeans.modules.uml.drawingarea.AbstractLabelManager.showLabel(AbstractLabelManager.java:146)
   at org.netbeans.modules.uml.diagrams.edges.BasicUMLLabelManager.updateLabel(BasicUMLLabelManager.java:318)
   at org.netbeans.modules.uml.diagrams.edges.AssociationLabelManager.propertyChange(AssociationLabelManager.java:186)
   at org.netbeans.modules.uml.diagrams.edges.AbstractUMLConnectionWidget.propertyChange(AbstractUMLConnectionWidget.java:104)
   at org.netbeans.modules.uml.diagrams.edges.AssociationConnector.propertyChange(AssociationConnector.java:266)
   at org.netbeans.modules.uml.drawingarea.DrawingAreaChangeHandler.elementChanged(DrawingAreaChangeHandler.java:219)
   at org.netbeans.modules.uml.drawingarea.DrawingAreaEventHandler$1ElementModified.run(DrawingAreaEventHandler.java:211)
   at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
   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)