java.util.ConcurrentModificationException
   at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
   at java.util.ArrayList$Itr.next(ArrayList.java:851)
   at org.netbeans.modules.extbrowser.plugins.ExternalBrowserPlugin.closeOtherDebuggingSessionsWithPageInspector(ExternalBrowserPlugin.java:282)
   at org.netbeans.modules.extbrowser.plugins.ExternalBrowserPlugin.access$1800(ExternalBrowserPlugin.java:85)
   at org.netbeans.modules.extbrowser.plugins.ExternalBrowserPlugin$BrowserTabDescriptor.init(ExternalBrowserPlugin.java:821)
   at org.netbeans.modules.extbrowser.plugins.ExternalBrowserPlugin$BrowserTabDescriptor.access$300(ExternalBrowserPlugin.java:723)
   at org.netbeans.modules.extbrowser.plugins.ExternalBrowserPlugin$2.run(ExternalBrowserPlugin.java:166)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1423)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)