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.api.javahelp.Help.showHelp(Help.java:75)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:0)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:597)
   at org.netbeans.modules.autoupdate.ui.PluginManagerUI.bHelpActionPerformed(PluginManagerUI.java:480)
   at org.netbeans.modules.autoupdate.ui.PluginManagerUI.access$1300(PluginManagerUI.java:96)
   at org.netbeans.modules.autoupdate.ui.PluginManagerUI$9.actionPerformed(PluginManagerUI.java:412)
   at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)
   at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)
   at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
   at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
   at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
   at java.awt.Component.processMouseEvent(Component.java:6352)
   at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
   at java.awt.Component.processEvent(Component.java:6117)
   at java.awt.Container.processEvent(Container.java:2085)
   at java.awt.Component.dispatchEventImpl(Component.java:4714)
   at java.awt.Container.dispatchEventImpl(Container.java:2143)
   at java.awt.Component.dispatchEvent(Component.java:4544)
   at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4621)
   at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4282)
   at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4212)
   at java.awt.Container.dispatchEventImpl(Container.java:2129)
   at java.awt.Window.dispatchEventImpl(Window.java:2478)
   at java.awt.Component.dispatchEvent(Component.java:4544)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:635)
   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)