Getting error with word_timestamps = true

[crsici]

I'm getting below error when running whisper in executor, it's not happen if max_worker=1. Please help if you have any idea!

default_thread_pool` = ThreadPoolExecutor(max_workers=3)

loop = asyncio.get_event_loop()

execFunction = partial(getModel().transcribe, fileName, 
temperature = temperature, word_timestamps = settings.word_timestamps, 
hallucination_silence_threshold = settings.hallucination_silence_threshold, 
**decode_options)

with default_thread_pool as executor:
    transcribe = await loop.run_in_executor(executor, execFunction)

File "root/.venv/lib/python3.9/site-packages/uvicorn/protocols/http/httptools_impl.py", line 409, in run_asgi
result = await app( # type: ignore[func-returns-value]
File "root/.venv/lib/python3.9/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in call
return await self.app(scope, receive, send)
File "root/.venv/lib/python3.9/site-packages/fastapi/applications.py", line 1054, in call
await super().call(scope, receive, send)
File "root/.venv/lib/python3.9/site-packages/starlette/applications.py", line 113, in call
await self.middleware_stack(scope, receive, send)
File "root/.venv/lib/python3.9/site-packages/starlette/middleware/errors.py", line 187, in call
raise exc
File "root/.venv/lib/python3.9/site-packages/starlette/middleware/errors.py", line 165, in call
await self.app(scope, receive, _send)
File "root/.venv/lib/python3.9/site-packages/starlette/middleware/exceptions.py", line 62, in call
await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
File "root/.venv/lib/python3.9/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
raise exc
File "root/.venv/lib/python3.9/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
await app(scope, receive, sender)
File "root/.venv/lib/python3.9/site-packages/starlette/routing.py", line 715, in call
await self.middleware_stack(scope, receive, send)
File "root/.venv/lib/python3.9/site-packages/starlette/routing.py", line 735, in app
await route.handle(scope, receive, send)
File "root/.venv/lib/python3.9/site-packages/starlette/routing.py", line 288, in handle
await self.app(scope, receive, send)
File "root/.venv/lib/python3.9/site-packages/starlette/routing.py", line 76, in app
await wrap_app_handling_exceptions(app, request)(scope, receive, send)
File "root/.venv/lib/python3.9/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
raise exc
File "root/.venv/lib/python3.9/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
await app(scope, receive, sender)
File "root/.venv/lib/python3.9/site-packages/starlette/routing.py", line 73, in app
response = await f(request)
File "root/.venv/lib/python3.9/site-packages/fastapi/routing.py", line 301, in app
raw_response = await run_endpoint_function(
File "root/.venv/lib/python3.9/site-packages/fastapi/routing.py", line 212, in run_endpoint_function
return await dependant.call(**values)
File "root/app/main.py", line 138, in test1
segments, outputLang = await transcribeFile("tests/ja3mb.mp3", {})
File "root/app/main.py", line 154, in transcribeFile
transcribe = await loop.run_in_executor(executor, func_with_kwargs)
File "/Users/lw12838/.pyenv/versions/3.9.9/lib/python3.9/concurrent/futures/thread.py", line 58, in run
result = self.fn(*self.args, **self.kwargs)
File "root/.venv/lib/python3.9/site-packages/whisper/transcribe.py", line 402, in transcribe
add_word_timestamps(
File "root/.venv/lib/python3.9/site-packages/whisper/timing.py", line 300, in add_word_timestamps
alignment = find_alignment(model, tokenizer, text_tokens, mel, num_frames, **kwargs)
File "root/.venv/lib/python3.9/site-packages/whisper/timing.py", line 197, in find_alignment
logits = model(mel.unsqueeze(0), tokens.unsqueeze(0))[0]
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1739, in _wrapped_call_impl
return self._call_impl(*args, **kwargs)
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1750, in _call_impl
return forward_call(*args, **kwargs)
File "root/.venv/lib/python3.9/site-packages/whisper/model.py", line 296, in forward
return self.decoder(tokens, self.encoder(mel))
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1739, in _wrapped_call_impl
return self._call_impl(*args, **kwargs)
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1750, in _call_impl
return forward_call(*args, **kwargs)
File "root/.venv/lib/python3.9/site-packages/whisper/model.py", line 242, in forward
x = block(x, xa, mask=self.mask, kv_cache=kv_cache)
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1739, in _wrapped_call_impl
return self._call_impl(*args, **kwargs)
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1750, in _call_impl
return forward_call(*args, **kwargs)
File "root/.venv/lib/python3.9/site-packages/whisper/model.py", line 169, in forward
x = x + self.cross_attn(self.cross_attn_ln(x), xa, kv_cache=kv_cache)[0]
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1739, in _wrapped_call_impl
return self._call_impl(*args, **kwargs)
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1845, in _call_impl
return inner()
File "root/.venv/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1806, in inner
hook_result = hook(self, args, result)
File "root/.venv/lib/python3.9/site-packages/whisper/timing.py", line 189, in
lambda _, ins, outs, index=i: QKs.setitem(index, outs[-1][0])
TypeError: 'NoneType' object is not subscriptable