java.lang.IllegalArgumentException: view is invalid
   at javax.help.search.MergingSearchEngine.merge(MergingSearchEngine.java:91)
   at javax.help.JHelpSearchNavigator.merge(JHelpSearchNavigator.java:168)
   at javax.help.plaf.basic.BasicSearchNavigatorUI.addSubHelpSets(BasicSearchNavigatorUI.java:275)
   at javax.help.plaf.basic.BasicSearchNavigatorUI.reloadData(BasicSearchNavigatorUI.java:225)
   at javax.help.plaf.basic.BasicSearchNavigatorUI.installUI(BasicSearchNavigatorUI.java:174)
   at javax.swing.JComponent.setUI(JComponent.java:662)
   at javax.help.JHelpNavigator.setUI(JHelpNavigator.java:257)
   at javax.help.JHelpNavigator.updateUI(JHelpNavigator.java:276)
   at javax.help.JHelpNavigator.<init>(JHelpNavigator.java:105)
   at javax.help.JHelpSearchNavigator.<init>(JHelpSearchNavigator.java:66)
   at javax.help.SearchView.createNavigator(SearchView.java:80)
   at javax.help.JHelp.setupNavigators(JHelp.java:148)
   at javax.help.JHelp.<init>(JHelp.java:126)
   at javax.help.JHelp.<init>(JHelp.java:76)
   at org.netbeans.modules.javahelp.JavaHelp.createJHelp(JavaHelp.java:919)
   at org.netbeans.modules.javahelp.JavaHelp.createAndDisplayJHelp(JavaHelp.java:495)
   at org.netbeans.modules.javahelp.JavaHelp.showHelp(JavaHelp.java:474)
   at org.netbeans.modules.javahelp.HelpCtxProcessor$ShortcutAction.actionPerformed(HelpCtxProcessor.java:160)
   at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)
   at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)
   at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
   at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
   at javax.swing.AbstractButton.doClick(AbstractButton.java:389)
   at com.apple.laf.ScreenMenuItem.actionPerformed(ScreenMenuItem.java:95)
   at java.awt.MenuItem.processActionEvent(MenuItem.java:627)
   at java.awt.MenuItem.processEvent(MenuItem.java:586)
   at java.awt.MenuComponent.dispatchEventImpl(MenuComponent.java:317)
   at java.awt.MenuComponent.dispatchEvent(MenuComponent.java:305)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:638)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:148)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)