java.lang.NullPointerException
        at javax.swing.plaf.basic.BasicTreeUI.ensureRowsAreVisible(BasicTreeUI.java:1861)
        at javax.swing.plaf.basic.BasicTreeUI.toggleExpandState(BasicTreeUI.java:2193)
        at apple.laf.CUIAquaTree.access$1200(CUIAquaTree.java:26)
        at apple.laf.CUIAquaTree$TreeArrowMouseInputHandler.mouseReleased(CUIAquaTree.java:341)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:232)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:231)
        at java.awt.Component.processMouseEvent(Component.java:5602)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3135)
        at java.awt.Component.processEvent(Component.java:5367)
        at java.awt.Container.processEvent(Container.java:2010)
        at java.awt.Component.dispatchEventImpl(Component.java:4068)
        at java.awt.Container.dispatchEventImpl(Container.java:2068)
        at java.awt.Component.dispatchEvent(Component.java:3903)
        at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4256)
        at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:3936)
        at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:3866)
        at java.awt.Container.dispatchEventImpl(Container.java:2054)
        at java.awt.Window.dispatchEventImpl(Window.java:1791)
        at java.awt.Component.dispatchEvent(Component.java:3903)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:190)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:176)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)