java.lang.NullPointerException
	at javax.swing.plaf.basic.BasicListUI$Actions.getNextPageIndex(BasicListUI.java:1897)
	at javax.swing.plaf.basic.BasicListUI$Actions.actionPerformed(BasicListUI.java:1715)
	at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1575)
	at javax.swing.JComponent.processKeyBinding(JComponent.java:2851)
	at javax.swing.JComponent.processKeyBindings(JComponent.java:2886)
	at javax.swing.JComponent.processKeyEvent(JComponent.java:2814)
	at java.awt.Component.processEvent(Component.java:5294)
	at java.awt.Container.processEvent(Container.java:1965)
	at java.awt.Component.dispatchEventImpl(Component.java:3958)
	at java.awt.Container.dispatchEventImpl(Container.java:2023)
	at java.awt.Component.dispatchEvent(Component.java:3806)
	at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1817)
	at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:682)
	at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:930)
	at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:808)
	at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:646)
	at java.awt.Component.dispatchEventImpl(Component.java:3844)
	at java.awt.Container.dispatchEventImpl(Container.java:2023)
	at java.awt.Window.dispatchEventImpl(Window.java:1768)
	at java.awt.Component.dispatchEvent(Component.java:3806)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:591)
[catch] at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:234)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)