java.util.ConcurrentModificationException
   at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
   at java.util.AbstractList$Itr.next(AbstractList.java:343)
   at org.netbeans.modules.xml.sync.DataObjectSyncSupport.addRepresentation(DataObjectSyncSupport.java:140)
   at org.netbeans.modules.xml.text.TextEditorSupport$3.stateChanged(TextEditorSupport.java:204)
   at org.openide.text.CloneableEditorSupport.fireStateChangeEvent(CloneableEditorSupport.java:2370)
   at org.openide.text.CloneableEditorSupport.fireDocumentChange(CloneableEditorSupport.java:2353)
   at org.openide.text.CloneableEditorSupport.access$900(CloneableEditorSupport.java:133)
   at org.openide.text.CloneableEditorSupport$3.doRun(CloneableEditorSupport.java:689)
   at org.openide.text.CloneableEditorSupport$3.run(CloneableEditorSupport.java:677)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.util.ConcurrentModificationException
   at org.openide.util.RequestProcessor$Task.schedule(RequestProcessor.java:1465)
   at org.openide.text.CloneableEditorSupport.prepareDocument(CloneableEditorSupport.java:743)
   at org.openide.text.CloneableEditorSupport.openDocumentImpl(CloneableEditorSupport.java:878)
   at org.openide.text.CloneableEditorSupport.openDocumentCheckIOE(CloneableEditorSupport.java:860)
   at org.openide.text.CloneableEditorSupport.openDocument(CloneableEditorSupport.java:842)
   at org.openide.text.DataEditorSupport.openDocument(DataEditorSupport.java:553)
   at org.netbeans.modules.versioning.diff.DiffSidebar.getText(DiffSidebar.java:1013)
   at org.netbeans.modules.versioning.diff.DiffSidebar.getText(DiffSidebar.java:920)
   at org.netbeans.modules.versioning.diff.DiffSidebar.access$1200(DiffSidebar.java:103)
   at org.netbeans.modules.versioning.diff.DiffSidebar$RefreshDiffTask.fetchOriginalContent(DiffSidebar.java:878)
   at org.netbeans.modules.versioning.diff.DiffSidebar$RefreshDiffTask.computeDiff(DiffSidebar.java:849)
   at org.netbeans.modules.versioning.diff.DiffSidebar$RefreshDiffTask.run(DiffSidebar.java:834)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1424)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1968)