java.lang.NullPointerException
        at org.netbeans.modules.uml.drawingarea.view.SelfLinkRouter.findTotalLinkToSelfBefore(SelfLinkRouter.java:129)
        at org.netbeans.modules.uml.drawingarea.view.SelfLinkRouter.routeConnection(SelfLinkRouter.java:63)
        at org.netbeans.api.visual.widget.ConnectionWidget.calculateRouting(ConnectionWidget.java:527)
        at org.netbeans.modules.visual.layout.ConnectionWidgetLayout.layout(ConnectionWidgetLayout.java:109)
        at org.netbeans.api.visual.widget.Widget.layout(Widget.java:1350)
        at org.netbeans.api.visual.widget.Widget.layout(Widget.java:1342)
        at org.netbeans.api.visual.widget.LayerWidget.layout(LayerWidget.java:86)
        at org.netbeans.api.visual.widget.Widget.layout(Widget.java:1342)
        at org.netbeans.api.visual.widget.Scene.layoutScene(Scene.java:312)
        at org.netbeans.api.visual.widget.Scene.validate(Scene.java:393)
        at org.netbeans.api.visual.widget.SceneComponent.processLocationOperator(SceneComponent.java:284)
        at org.netbeans.api.visual.widget.SceneComponent.mouseDragged(SceneComponent.java:167)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:319)
        at java.awt.Component.processMouseMotionEvent(Component.java:6154)
        at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3294)
        at java.awt.Component.processEvent(Component.java:5875)
        at java.awt.Container.processEvent(Container.java:2105)
        at java.awt.Component.dispatchEventImpl(Component.java:4467)
        at java.awt.Container.dispatchEventImpl(Container.java:2163)
        at java.awt.Component.dispatchEvent(Component.java:4293)
        at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4461)
        at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4142)
        at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4055)
        at java.awt.Container.dispatchEventImpl(Container.java:2149)
        at java.awt.Window.dispatchEventImpl(Window.java:2478)
        at java.awt.Component.dispatchEvent(Component.java:4293)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:604)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:275)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:200)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:190)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:185)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:177)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:138)