Update app.py

app.py

@@ -31,8 +31,10 @@ def respond(openai_apikey, chat_history):
         messages=re_messages,
         temperature=0.7
     )
-
-    chat_history[-1][1] = ""
+    if not chat_history:
+        chat_history.apend([','])
+    if chat_history[-1][1] is None:
+        chat_history[-1][1] = ""
     for re_chunk in re_chat_completion.choices:
         chat_history[-1][1] += re_chunk.delta.get("content", "")