java.lang.NullPointerException
   at javax.swing.plaf.basic.BasicTreeUI.updateSize(BasicTreeUI.java:0)
   at javax.swing.plaf.basic.BasicTreeUI$ComponentHandler.actionPerformed(BasicTreeUI.java:0)
   at javax.swing.Timer.fireActionPerformed(Timer.java:0)
   at javax.swing.Timer$DoPostEvent.run(Timer.java:0)
   at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:0)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:0)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:131)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:0)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:0)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:0)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:0)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:0)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:0)