Clear the identifier_number on identifier reset (fixes #3353)

CHANGELOG

@@ -40,6 +40,7 @@ Motions:
 - Added inline Editing for motion reason [#3361].
 - Added multiselect filter for motion comments [#3372].
 - Added support for pinning personal notes to the window [#3360].
+- Clear identifier on state reset [#3356].
 
 Elections:
 - Added pagination for list view [#3393].

openslides/motions/models.py

@@ -581,13 +581,20 @@ class Motion(RESTModelMixin, models.Model):
 
     def reset_state(self, workflow=None):
         """
-        Set the state to the default state.
+        Set the state to the default state. If an identifier was set
+        automatically, reset the identifier and identifier_number.
 
         'workflow' can be a workflow, an id of a workflow or None.
 
         If the motion is new and workflow is None, it chooses the default
         workflow from config.
         """
+
+        # The identifier is set automatically.
+        if config['motions_identifier'] is not 'manually':
+            self.identifier = ''
+            self.identifier_number = None
+
         if type(workflow) is int:
             workflow = Workflow.objects.get(pk=workflow)