response_text = assistant_responses[-1].content if assistant_responses else "抱歉，助手有點累，好像睡著了，請稍後再試。"

app.py

@@ -1049,7 +1049,7 @@ def chat_with_youtube_transcript(youtube_id, thread_id, user_message, chat_histo
     if run_status == "completed":
         messages = client.beta.threads.messages.list(thread_id=thread.id)
         assistant_responses = [msg for msg in messages.data if msg.role == "assistant"]
-        response_text = assistant_responses[-1].content if assistant_responses
+        response_text = assistant_responses[-1].content if assistant_responses else "抱歉，助手有點累，好像睡著了，請稍後再試。"
     else:
         response_text = "抱歉，助手有點累，好像睡著了，請稍後再試。"