Actual behavior:
Selecting some right-click context menu action of a data node in the datamanger does not perform any action or leads to a crash of the MITK workbench.
Some do not work, because the datamanager has not been set before (e.g. QmitkCreateMultiLabelSegmentationAction, QmitkConvertToMultiLabelSegmentationAction).
QmitkStatisticsAction does not work, because it doesn't exist anymore.
Should be fixed with T20196. However, QmitkStatisticsAction seems to be superfluous here.
Could you check whether this still happens? I can not reproduce any behaviour that would fit with what you describe, however I am still somewhat unclear on what you actually did.
As I wrote, this happened on an old master and was already taken care of with the above mentioned task by Stefan. Still the 'QmitkStatisticsAction' is checked in the 'QmitkDataManagerView'-class, although the 'QmitkStatisticsAction' does not exist anymore?
The original issue was resolved, keep an eye on T22435: QmitkDataManager checks for deprecated QmitkStatisticsAction for the QmitkStatisticsAction fix.