fix: persist upstream streaming error lines by awaiting the message upsert (#27365)

The branch that normalizes plain JSON error lines from streaming upstreams (lines without the SSE data: prefix) called Chats.upsert_message_to_chat_by_id_and_message_id without await. The coroutine was never executed, so the error was never written to the chat and Python emitted a "coroutine was never awaited" RuntimeWarning instead. The frontend still received the error event, but after a reload the message showed no trace of the failure.

The parallel error-persist branch further down the same handler already awaits the call; this aligns the two.

backend/open_webui/utils/middleware.py

@@ -4116,7 +4116,7 @@ async def streaming_chat_response_handler(response, ctx):
                                 raw_error = raw_obj.get('error') if isinstance(raw_obj, dict) else None
                                 if raw_error:
                                     try:
-                                        Chats.upsert_message_to_chat_by_id_and_message_id(
+                                        await Chats.upsert_message_to_chat_by_id_and_message_id(
                                             metadata['chat_id'],
                                             metadata['message_id'],
                                             {