java.lang.AssertionError
        at org.openide.text.CloneableEditorSupport.getOpenedPanes(CloneableEditorSupport.java:1058)
        at org.netbeans.modules.mobility.editor.DocumentPreprocessor.repaintDocument(DocumentPreprocessor.java:214)
        at org.netbeans.modules.mobility.editor.DocumentPreprocessor.updateBlockChain(DocumentPreprocessor.java:206)
        at org.netbeans.modules.mobility.editor.DocumentPreprocessor.<init>(DocumentPreprocessor.java:117)
        at org.netbeans.modules.mobility.editor.pub.J2MEDataObject$J2MEEditorSupport.createEditorKit(J2MEDataObject.java:346)
        at org.openide.text.CloneableEditorSupport.prepareDocument(CloneableEditorSupport.java:596)
        at org.openide.text.CloneableEditorSupport.openDocumentImpl(CloneableEditorSupport.java:824)
        at org.openide.text.CloneableEditorSupport.openDocumentCheckIOE(CloneableEditorSupport.java:806)
        at org.openide.text.CloneableEditorSupport.openDocument(CloneableEditorSupport.java:786)
        at org.openide.text.DataEditorSupport.openDocument(DataEditorSupport.java:404)
        at org.netbeans.modules.versioning.diff.DiffSidebar.createReader(DiffSidebar.java:800)
        at org.netbeans.modules.versioning.diff.DiffSidebar.getText(DiffSidebar.java:772)
        at org.netbeans.modules.versioning.diff.DiffSidebar.access$900(DiffSidebar.java:88)
        at org.netbeans.modules.versioning.diff.DiffSidebar$RefreshDiffTask.fetchOriginalContent(DiffSidebar.java:715)
        at org.netbeans.modules.versioning.diff.DiffSidebar$RefreshDiffTask.computeDiff(DiffSidebar.java:688)
        at org.netbeans.modules.versioning.diff.DiffSidebar$RefreshDiffTask.run(DiffSidebar.java:678)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:573)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1005)