fix: emit [DONE] for AsyncGenerator pipe returns

Author: Algorithm5838

backend/open_webui/functions.py

@@ -318,7 +318,7 @@ async def stream_content():
                 async for line in res:
                     yield process_line(form_data, line)
 
-            if isinstance(res, str) or isinstance(res, Generator):
+            if isinstance(res, str) or isinstance(res, Generator) or isinstance(res, AsyncGenerator):
                 finish_message = openai_chat_chunk_message_template(form_data['model'], '')
                 finish_message['choices'][0]['finish_reason'] = 'stop'
                 yield f'data: {json.dumps(finish_message)}\n\n'