java.lang.AssertionError: tn must be our child!
        at org.openide.explorer.view.VisualizerChildren.recomputeIndexes(VisualizerChildren.java:94)
        at org.openide.explorer.view.VisualizerChildren.getIndex(VisualizerChildren.java:161)
        at org.openide.explorer.view.VisualizerNode.getIndex(VisualizerNode.java:276)
        at javax.swing.tree.DefaultTreeModel.getIndexOfChild(DefaultTreeModel.java:142)
        at javax.swing.tree.FixedHeightLayoutCache.getVisiblePathsFrom(FixedHeightLayoutCache.java:269)
        at javax.swing.plaf.basic.BasicTreeUI.paint(BasicTreeUI.java:1138)
        at javax.swing.plaf.ComponentUI.update(ComponentUI.java:143)
        at javax.swing.JComponent.paintComponent(JComponent.java:763)
        at javax.swing.JComponent.paint(JComponent.java:1027)
        at org.openide.explorer.view.TreeView$ExplorerTree.access$1201(TreeView.java:1557)
        at org.openide.explorer.view.TreeView$ExplorerTree.guardedPaint(TreeView.java:1746)
        at org.openide.explorer.view.TreeView$ExplorerTree.access$1600(TreeView.java:1557)
        at org.openide.explorer.view.TreeView$ExplorerTree$GuardedActions.run(TreeView.java:2084)
        at org.openide.util.Mutex.readAccess(Mutex.java:285)
        at org.openide.explorer.view.TreeView$ExplorerTree$GuardedActions.<init>(TreeView.java:2077)
        at org.openide.explorer.view.TreeView$ExplorerTree.paint(TreeView.java:1681)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JViewport.paint(JViewport.java:747)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JSplitPane.paintChildren(JSplitPane.java:1026)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at org.netbeans.swing.tabcontrol.TabbedContainer.paint(TabbedContainer.java:968)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at org.netbeans.core.windows.view.ui.MultiSplitPane.paint(MultiSplitPane.java:323)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at org.netbeans.core.windows.view.ui.MultiSplitPane.paint(MultiSplitPane.java:323)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JLayeredPane.paint(JLayeredPane.java:564)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JLayeredPane.paint(JLayeredPane.java:564)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paintToOffscreen(JComponent.java:5129)
        at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1382)
        at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1313)
        at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:301)
        at javax.swing.RepaintManager.paint(RepaintManager.java:1128)
        at javax.swing.JComponent.paint(JComponent.java:1013)
        at java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)
        at sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)
        at sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)
        at java.awt.Container.paint(Container.java:1797)
        at org.netbeans.core.windows.view.ui.MainWindow.paint(MainWindow.java:577)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:734)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:679)
        at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:659)
        at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:128)
        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:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)