java.lang.IllegalArgumentException: Comparison method violates its general contract!
   at java.util.TimSort.mergeLo(TimSort.java:773)
   at java.util.TimSort.mergeAt(TimSort.java:510)
   at java.util.TimSort.mergeCollapse(TimSort.java:435)
   at java.util.TimSort.sort(TimSort.java:241)
   at java.util.Arrays.sort(Arrays.java:1438)
   at org.netbeans.modules.uml.ui.support.projecttreesupport.ProjectTreeBuilderImpl.sort(ProjectTreeBuilderImpl.java:361)
   at org.netbeans.modules.uml.ui.support.projecttreesupport.ProjectTreeBuilderImpl.retrieveChildItemsSorted(ProjectTreeBuilderImpl.java:401)
   at org.netbeans.modules.uml.reporting.ReportTask.processChildren(ReportTask.java:341)
   at org.netbeans.modules.uml.reporting.ReportTask.loadDataElement(ReportTask.java:322)
   at org.netbeans.modules.uml.reporting.ReportTask.processChildren(ReportTask.java:358)
   at org.netbeans.modules.uml.reporting.ReportTask.loadDataElement(ReportTask.java:322)
   at org.netbeans.modules.uml.reporting.ReportTask.processChildren(ReportTask.java:358)
   at org.netbeans.modules.uml.reporting.ReportTask.loadDataElement(ReportTask.java:322)
   at org.netbeans.modules.uml.reporting.ReportTask.processChildren(ReportTask.java:358)
   at org.netbeans.modules.uml.reporting.ReportTask.loadDataElement(ReportTask.java:322)
   at org.netbeans.modules.uml.reporting.ReportTask.processChildren(ReportTask.java:358)
   at org.netbeans.modules.uml.reporting.ReportTask.loadDataElement(ReportTask.java:322)
   at org.netbeans.modules.uml.reporting.ReportTask.processChildren(ReportTask.java:358)
   at org.netbeans.modules.uml.reporting.ReportTask.loadDataElement(ReportTask.java:322)
   at org.netbeans.modules.uml.reporting.ReportTask.processChildren(ReportTask.java:358)
   at org.netbeans.modules.uml.reporting.ReportTask.loadDataElement(ReportTask.java:322)
   at org.netbeans.modules.uml.reporting.ReportTask.generateReport(ReportTask.java:205)
   at org.netbeans.modules.uml.reporting.ReportTask.run(ReportTask.java:185)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
   at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
   at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)