fix(internal_user_endpoints.py): add check on sortby value

Author: krrishdholakia

litellm/proxy/management_endpoints/internal_user_endpoints.py

@@ -1043,7 +1043,12 @@ async def get_users(
  where_conditions = {k: v for k, v in where_conditions.items() if v is not None}
 
  # Build order_by conditions
- order_by: Optional[Dict[str, str]] = _validate_sort_params(sort_by, sort_order)
+
+ order_by: Optional[Dict[str, str]] = (
+ _validate_sort_params(sort_by, sort_order)
+ if sort_by is not None and isinstance(sort_by, str)
+ else None
+ )
 
  users = await prisma_client.db.litellm_usertable.find_many(
  where=where_conditions,