avoid double entries in accessed table

pandora/user/views.py

@@ -794,6 +794,7 @@ def setUI(request, data):
 
     if data.get('item'):
         item = get_object_or_404_json(Item, public_id=data['item'])
+        with transaction.atomic():
             if request.user.is_authenticated():
                 access, created = Access.objects.get_or_create(item=item, user=request.user)
             else: