问一个关于帮助文档的问题

feasky

当添加某一帮助文件到收藏夹的时候，出现以下错误，哪位能帮在下解决一下。

fatal error.
－Type：IllegalArgumentException

以下是详细信息：
Exception:
  java.lang.IllegalArgumentException: argument is null
  (rethrown as com.femlab.util.FlFatalException)
Messages:
  Fatal error.

  Type: IllegalArgumentException

Stack trace:

  at javax.swing.tree.DefaultMutableTreeNode.getIndex(DefaultMutableTreeNode.java:261)

  at javax.help.plaf.basic.BasicFavoritesNavigatorUI.treeNodesInserted(BasicFavoritesNavigatorUI.java:846)

  at javax.swing.tree.DefaultTreeModel.fireTreeNodesInserted(DefaultTreeModel.java:497)

  at javax.swing.tree.DefaultTreeModel.nodesWereInserted(DefaultTreeModel.java:294)

  at javax.swing.tree.DefaultTreeModel.insertNodeInto(DefaultTreeModel.java:223)

  at javax.help.plaf.basic.BasicFavoritesNavigatorUI$AddAction.actionPerformed(BasicFavoritesNavigatorUI.java:942)

  at javax.help.FavoritesAction.actionPerformed(FavoritesAction.java:68)

  at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1786)

  at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1839)

  at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)

  at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)

  at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:245)

  at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:231)

  at java.awt.Component.processMouseEvent(Component.java:5100)

  at java.awt.Component.processEvent(Component.java:4897)

  at java.awt.Container.processEvent(Container.java:1569)

  at java.awt.Component.dispatchEventImpl(Component.java:3615)

  at java.awt.Container.dispatchEventImpl(Container.java:1627)

  at java.awt.Component.dispatchEvent(Component.java:3477)

  at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483)

  at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)

  at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)

  at java.awt.Container.dispatchEventImpl(Container.java:1613)

  at java.awt.Window.dispatchEventImpl(Window.java:1606)

  at java.awt.Component.dispatchEvent(Component.java:3477)

  at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)

  at com.femlab.gui.FlEventQueue.dispatchEvent(FlEventQueue.java:24)

  at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)

  at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)

  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)

  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)

  at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)