Update app.py

app.py

@@ -137,8 +137,10 @@ with gr.Blocks() as demo:
     def bot(history, max_new_tokens, temperature, top_p, system_prompt):
         messages = [{"role": "system", "content": system_prompt}]
         for user, bot in history:
-            messages.append({"role": "user", "content": user})
-            messages.append({"role": "assistant", "content": bot})
+            if user is not None:
+                messages.append({"role": "user", "content": user})
+            if bot is not None:
+                messages.append({"role": "assistant", "content": bot})
 
         history[-1][1] = ""
         response = openai.ChatCompletion.create(