Update app.py

app.py

@@ -172,7 +172,8 @@ def create_demo():
         async def process_input(space_system_description, history, api_key):
             nonlocal space_crew
             if not api_key:
-                return [{"role": "assistant", "content": "Please provide an OpenAI API key."}]
+                yield [{"role": "assistant", "content": "Please provide an OpenAI API key."}]
+                return
 
             if space_crew is None:
                 space_crew = SpaceSystemCrew(api_key=api_key)