update default model

app.py

@@ -97,7 +97,7 @@ with gr.Blocks() as demo:
     def change_prompt(prompt_set_name, prompt_name):
         return gr.update(value=prompt_set_list[prompt_set_name][prompt_name])
 
-    def user(user_message, history):
+    def user(user_message, history = []):
         return gr.update(value="", interactive=False), history + [[user_message, None]]
 
     def bot(history, model_name, provider_name, system_msg, chat_mode):