java.lang.AssertionError
        at org.netbeans.modules.form.layoutdesign.LayoutModel.addInterval(LayoutModel.java:319)
        at org.netbeans.modules.form.layoutdesign.LayoutFeeder.addToGroup(LayoutFeeder.java:1043)
        at org.netbeans.modules.form.layoutdesign.LayoutFeeder.addInterval(LayoutFeeder.java:754)
        at org.netbeans.modules.form.layoutdesign.LayoutFeeder.add(LayoutFeeder.java:311)
        at org.netbeans.modules.form.layoutdesign.LayoutDesigner.addComponents(LayoutDesigner.java:825)
        at org.netbeans.modules.form.layoutdesign.LayoutDesigner.endMoving(LayoutDesigner.java:750)
        at org.netbeans.modules.form.HandleLayer$ResizeComponentDrag.end(HandleLayer.java:2826)
        at org.netbeans.modules.form.HandleLayer$ComponentDrag.end(HandleLayer.java:2467)
        at org.netbeans.modules.form.HandleLayer.endDragging(HandleLayer.java:1258)
        at org.netbeans.modules.form.HandleLayer.mouseReleased(HandleLayer.java:1814)
        at java.awt.Component.processMouseEvent(Component.java:6341)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3311)
        at java.awt.Component.processEvent(Component.java:6106)
        at java.awt.Container.processEvent(Container.java:2122)
        at java.awt.Component.dispatchEventImpl(Component.java:4701)
        at java.awt.Container.dispatchEventImpl(Container.java:2180)
        at java.awt.Component.dispatchEvent(Component.java:4527)
        at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4706)
        at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4369)
        at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4299)
        at java.awt.Container.dispatchEventImpl(Container.java:2166)
        at java.awt.Window.dispatchEventImpl(Window.java:2611)
        at java.awt.Component.dispatchEvent(Component.java:4527)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:618)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:125)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:286)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:191)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:186)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:178)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:139)