Sync with latest openai lib

Signed-off-by: Yasir Aris M <git@yasirdev.my.id>

misskaty/plugins/chatbot_ai.py

@@ -68,6 +68,8 @@ async def openai_chatbot(_, ctx: Message, strings):
             stream=True,
         )
         async for chunk in response:
+            if not chunk.choices[0].delta:
+                continue
             num += 1
             answer += chunk.choices[0].delta.content
             if num == 30: