and here is the log file, thank you!
[ERROR][Python] 10.11.2020 17:00:53 [Python] (/home/lalageh/Slicer-4.11.20200930-linux-amd64/lib/Slicer-4.11/qt-scripted-modules/SubjectHierarchyPlugins/SegmentEditorSubjectHierarchyPlugin.py:124) - Invalid current item
[CRITICAL][Qt] 10.11.2020 17:00:53 [] (unknown:0) - virtual void qSlicerSubjectHierarchyRegisterPlugin::showContextMenuActionsForItem(vtkIdType) : Invalid current item
[CRITICAL][Stream] 10.11.2020 17:00:53 [] (unknown:0) - Invalid current item
[CRITICAL][Qt] 10.11.2020 17:00:58 [] (unknown:0) - void qSlicerSubjectHierarchyDICOMPlugin::openDICOMExportDialog() : Invalid current item