Transition.py: when generating guard, create an empty guard first.

product/ERP5Workflow/Document/Transition.py

@@ -93,10 +93,7 @@ class Transition(IdAsReferenceMixin("transition_", "prefix"), XMLObject):
 
   def generateGuard(self):
     if self.guard is None:
-      self.guard = Guard(permissions=self.getPermissionList(),
-                    roles=self.getRoleList(),
-                    groups=self.getGroupList(),
-                    expr=Expression(self.getExpression()))
+      self.guard = Guard()
 
     if self.getRoleList() is not None:
       self.guard.roles = self.getRoleList()