Fix append

app.py

@@ -79,7 +79,7 @@ def generate_for_prompt(input_text, state, ret_scale_factor, max_nm_rets, num_wo
                 response += f'<img src="/file={filename}">'
 
     # TODO(jykoh): Persist image inputs.
-    chat_history = model_inputs + ' '.join([s for s in model_outputs if type(s) == str]) + '\n'
+    chat_history = model_inputs + [' '.join([s for s in model_outputs if type(s) == str]) + '\n']
     conversation.append((input_text, response))
 
     # Set input image to None.