java.lang.AssertionError: Unregister asymmetrically called
        at org.openide.explorer.view.ViewTooltips.unregister(ViewTooltips.java:130)
        at org.openide.explorer.view.TreeView$ExplorerTree.removeNotify(TreeView.java:1562)
        at java.awt.Container.removeNotify(Container.java:2619)
        at javax.swing.JComponent.removeNotify(JComponent.java:4699)
        at java.awt.Container.removeNotify(Container.java:2619)
        at javax.swing.JComponent.removeNotify(JComponent.java:4699)
        at org.openide.explorer.view.TreeView.removeNotify(TreeView.java:627)
        at java.awt.Container.removeNotify(Container.java:2619)
        at javax.swing.JComponent.removeNotify(JComponent.java:4699)
        at org.netbeans.beaninfo.ExplorerPanel.removeNotify(ExplorerPanel.java:76)
        at java.awt.Container.removeNotify(Container.java:2619)
        at javax.swing.JComponent.removeNotify(JComponent.java:4699)
        at java.awt.Container.removeNotify(Container.java:2619)
        at javax.swing.JComponent.removeNotify(JComponent.java:4699)
        at org.netbeans.swing.tabcontrol.TabbedContainer.removeNotify(TabbedContainer.java:955)
        at java.awt.Container.removeNotify(Container.java:2619)
        at javax.swing.JComponent.removeNotify(JComponent.java:4699)
        at java.awt.Container.remove(Container.java:1136)
        at java.awt.Container.remove(Container.java:1203)
        at java.awt.Container.addImpl(Container.java:1032)
        at java.awt.Container.add(Container.java:352)
        at org.netbeans.core.windows.view.ui.MultiSplitPane$MultiSplitLayout.layoutCells(MultiSplitPane.java:643)
        at org.netbeans.core.windows.view.ui.MultiSplitPane$MultiSplitLayout.layoutContainer(MultiSplitPane.java:620)
        at java.awt.Container.layout(Container.java:1432)
        at java.awt.Container.doLayout(Container.java:1421)
        at java.awt.Container.validateTree(Container.java:1519)
        at java.awt.Container.validateTree(Container.java:1526)
        at java.awt.Container.validate(Container.java:1491)
        at org.netbeans.core.windows.view.ui.DesktopImpl$LayeredLayout.layoutContainer(DesktopImpl.java:454)
        at java.awt.Container.layout(Container.java:1432)
        at java.awt.Container.doLayout(Container.java:1421)
        at java.awt.Container.validateTree(Container.java:1519)
        at java.awt.Container.validateTree(Container.java:1526)
        at java.awt.Container.validateTree(Container.java:1526)
        at java.awt.Container.validateTree(Container.java:1526)
        at java.awt.Container.validateTree(Container.java:1526)
        at java.awt.Container.validate(Container.java:1491)
        at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:635)
        at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:127)
        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)