runtime error

Exit code: 1. Reason: l/lib/python3.10/site-packages/gradio/routes.py", line 1651, in startup_events await app.get_blocks().run_extra_startup_events() File "/usr/local/lib/python3.10/site-packages/gradio/blocks.py", line 3116, in run_extra_startup_events await startup_event() File "/usr/local/lib/python3.10/site-packages/gradio/helpers.py", line 470, in _start_caching await self.cache() File "/usr/local/lib/python3.10/site-packages/gradio/helpers.py", line 536, in cache prediction = await self.root_block.process_api( File "/usr/local/lib/python3.10/site-packages/gradio/blocks.py", line 2193, in process_api result = await self.call_function( File "/usr/local/lib/python3.10/site-packages/gradio/blocks.py", line 1702, in call_function prediction = await fn(*processed_input) File "/usr/local/lib/python3.10/site-packages/gradio/utils.py", line 861, in async_wrapper response = await f(*args, **kwargs) File "/usr/local/lib/python3.10/site-packages/gradio/helpers.py", line 503, in get_final_item async for x in self.fn(*args): # noqa: B007 # type: ignore File "/usr/local/lib/python3.10/site-packages/gradio/chat_interface.py", line 1087, in _examples_stream_fn async for response in generator: File "/usr/local/lib/python3.10/site-packages/gradio/utils.py", line 733, in __anext__ return await anyio.to_thread.run_sync( File "/usr/local/lib/python3.10/site-packages/anyio/to_thread.py", line 56, in run_sync return await get_async_backend().run_sync_in_worker_thread( File "/usr/local/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 2485, in run_sync_in_worker_thread return await future File "/usr/local/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 976, in run result = context.run(func, *args) File "/usr/local/lib/python3.10/site-packages/gradio/utils.py", line 716, in run_sync_iterator_async return next(iterator) File "/app/app.py", line 60, in respond response += token TypeError: can only concatenate str (not "NoneType") to str

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