Workflow.py: in showAsXML, rewrite variable action's expression to getReference.

product/ERP5Workflow/Document/Workflow.py

@@ -887,6 +887,10 @@ class Workflow(IdAsReferenceMixin("workflow_", "prefix"), XMLObject):
         if property_value is None or property_value ==() or property_value == []:
           property_value = ''
         sub_object.text = str(property_value)
+        # for a very specific case, action return the reference of transition,
+        # but in XML should show the same expression as in DC workflow.
+        if vdef.getId() == 'variable_action' and property_id == 'default_expr':
+          sub_object.text = str('transition/getId|nothing')
 
     # 4. Worklist as XML
     worklist_reference_list = []