workflows: task_counter value check
workflows: task_counter value check

* Checks if the task_counter parameter is a list when saving
  an BibWorkflowObject. It is required to avoid a problem with the
  underlying workflow engine.

Signed-off-by: Jan Aage Lavik <8d55e006a1b29770f275a5c59a7341f17f8e69d5@cern.ch>

tiborsimko/invenio,inveniosoftware/invenio,tiborsimko/invenio,inveniosoftware/invenio