fixed exception during file monitoring

[stlanger]

I have received the following error after renaming a PDF file in Docear (see #290)

STDERR: Exception occurred during event dispatching:
STDERR: java.lang.ClassCastException: com.sun.java.swing.plaf.nimbus.DerivedColor$UIResource cannot be cast to com.sun.java.swing.Painter
STDERR: at com.sun.java.swing.plaf.nimbus.NimbusStyle.getBackgroundPainter(NimbusStyle.java:829)
STDERR: at com.sun.java.swing.plaf.nimbus.SynthPainterImpl.paintBackground(SynthPainterImpl.java:85)
STDERR: at com.sun.java.swing.plaf.nimbus.SynthPainterImpl.paintPanelBackground(SynthPainterImpl.java:943)
STDERR: at javax.swing.plaf.synth.SynthPanelUI.update(SynthPanelUI.java:95)
STDERR: at javax.swing.JComponent.paintComponent(JComponent.java:752)
STDERR: at javax.swing.JComponent.paint(JComponent.java:1029)
STDERR: at javax.swing.JComponent.paintToOffscreen(JComponent.java:5124)
STDERR: at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:278)
STDERR: at javax.swing.RepaintManager.paint(RepaintManager.java:1224)
STDERR: at javax.swing.JComponent._paintImmediately(JComponent.java:5072)
STDERR: at javax.swing.JComponent.paintImmediately(JComponent.java:4882)
STDERR: at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:785)
STDERR: at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:713)
STDERR: at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:693)
STDERR: at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:125)
STDERR: at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
STDERR: at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:641)
STDERR: at java.awt.EventQueue.access$000(EventQueue.java:84)
STDERR: at java.awt.EventQueue$1.run(EventQueue.java:602)
STDERR: at java.awt.EventQueue$1.run(EventQueue.java:600)
STDERR: at java.security.AccessController.doPrivileged(Native Method)
STDERR: at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
STDERR: at java.awt.EventQueue.dispatchEvent(EventQueue.java:611)
STDERR: at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
STDERR: at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
STDERR: at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:178)
STDERR: at java.awt.Dialog$1.run(Dialog.java:1046)
STDERR: at java.awt.Dialog$3.run(Dialog.java:1098)
STDERR: at java.security.AccessController.doPrivileged(Native Method)
STDERR: at java.awt.Dialog.show(Dialog.java:1096)
STDERR: at java.awt.Component.show(Component.java:1584)
STDERR: at java.awt.Component.setVisible(Component.java:1536)
STDERR: at java.awt.Window.setVisible(Window.java:842)
STDERR: at java.awt.Dialog.setVisible(Dialog.java:986)
STDERR: at org.docear.plugin.core.ui.SwingWorkerDialog.showDialog(SwingWorkerDialog.java:77)
STDERR: at org.docear.plugin.pdfutilities.actions.AbstractMonitoringAction.updateNodesAgainstMonitoringDir(AbstractMonitoringAction.java:64)
STDERR: at org.docear.plugin.pdfutilities.listener.DocearNodeMouseMotionListener.mouseClicked(DocearNodeMouseMotionListener.java:130)
STDERR: at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:253)
STDERR: at java.awt.Component.processMouseEvent(Component.java:6291)
STDERR: at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
STDERR: at java.awt.Component.processEvent(Component.java:6053)
STDERR: at java.awt.Container.processEvent(Container.java:2041)
STDERR: at java.awt.Component.dispatchEventImpl(Component.java:4651)
STDERR: at java.awt.Container.dispatchEventImpl(Container.java:2099)
STDERR: at java.awt.Component.dispatchEvent(Component.java:4481)
STDERR: at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577)
STDERR: at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4247)
STDERR: at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
STDERR: at java.awt.Container.dispatchEventImpl(Container.java:2085)
STDERR: at java.awt.Window.dispatchEventImpl(Window.java:2478)
STDERR: at java.awt.Component.dispatchEvent(Component.java:4481)
STDERR: at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:643)
STDERR: at java.awt.EventQueue.access$000(EventQueue.java:84)
STDERR: at java.awt.EventQueue$1.run(EventQueue.java:602)
STDERR: at java.awt.EventQueue$1.run(EventQueue.java:600)
STDERR: at java.security.AccessController.doPrivileged(Native Method)
STDERR: at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
STDERR: at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
STDERR: at java.awt.EventQueue$2.run(EventQueue.java:616)
STDERR: at java.awt.EventQueue$2.run(EventQueue.java:614)
STDERR: at java.security.AccessController.doPrivileged(Native Method)
STDERR: at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
STDERR: at java.awt.EventQueue.dispatchEvent(EventQueue.java:613)
STDERR: at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
STDERR: at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
STDERR: at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
STDERR: at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
STDERR: at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
STDERR: at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)Jan 7, 2014 12:57:09 PM org.freeplane.core.util.LogUtils info