Exception in thread "AWT-EventQueue-0" java.lang.AssertionError: component is not JInternalFrame or JInternalFrame.JDesktopIcon
        at com.sun.java.swing.plaf.gtk.Metacity.updateFrameGeometry(Metacity.java:1476)
        at com.sun.java.swing.plaf.gtk.Metacity.paintButtonBackground(Metacity.java:219)
        at com.sun.java.swing.plaf.gtk.GTKPainter.paintButtonBackground(GTKPainter.java:270)
        at javax.swing.plaf.synth.SynthButtonUI.paintBackground(SynthButtonUI.java:301)
        at javax.swing.plaf.synth.SynthButtonUI.update(SynthButtonUI.java:256)
        at javax.swing.JComponent.paintComponent(JComponent.java:777)
        at javax.swing.JComponent.paint(JComponent.java:1053)
        at javax.swing.JComponent.paintChildren(JComponent.java:886)
        at javax.swing.JComponent.paint(JComponent.java:1062)
        at javax.swing.JComponent.paintChildren(JComponent.java:886)
        at javax.swing.JComponent.paint(JComponent.java:1062)
        at javax.swing.JComponent.paintChildren(JComponent.java:886)
        at javax.swing.JComponent.paint(JComponent.java:1062)
        at javax.swing.JLayeredPane.paint(JLayeredPane.java:586)
        at javax.swing.JComponent.paintToOffscreen(JComponent.java:5228)
        at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:290)
        at javax.swing.RepaintManager.paint(RepaintManager.java:1252)
        at javax.swing.JComponent._paintImmediately(JComponent.java:5176)
        at javax.swing.JComponent.paintImmediately(JComponent.java:4987)
        at javax.swing.RepaintManager$3.run(RepaintManager.java:811)
        at javax.swing.RepaintManager$3.run(RepaintManager.java:794)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:794)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:769)
        at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:718)
        at javax.swing.RepaintManager.access$1100(RepaintManager.java:62)
        at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1680)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
        at java.awt.EventQueue.access$400(EventQueue.java:97)
        at java.awt.EventQueue$3.run(EventQueue.java:697)
        at java.awt.EventQueue$3.run(EventQueue.java:691)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)