#112 Migration enhance

* fixes bug in migration
* adds check to migration which raises error before data loss might happen

compensation/migrations/0004_auto_20220210_1402.py

@@ -9,9 +9,12 @@ def migrate_actions(apps, schema_editor):
 
     for action in actions:
         action_type = action.action_type or []
-        action.action_type_tmp.set(action_type)
+        action.action_type_tmp.set([action_type])
         action.save()
 
+        if not action.action_type_tmp.count() > 0:
+            raise ValueError("Migration of actions did not work! Stoped before data loss!")
+
 
 class Migration(migrations.Migration):