LangchainTracer.on_llm_error callback: IndexError('list index out of range')
Labels: name: area: memory, name: auto:bug

### System Info

This is a random occurrence. Maybe after I ask many questions
when it happen,   Only clear the memory can recover.

the code to ask:
                async for chunk in runnable.astream(   #or call  astream_log
                        question,
                        config
                ):
                    await res.stream_token(chunk)
error information:

2024-01-09 13:32:02 - Error in LangchainTracer.on_llm_error callback: IndexError('list index out of range')
2024-01-09 13:32:02 - 
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/chainlit/utils.py", line 39, in wrapper
    return await user_function(**params_values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/rag-app/main.py", line 164, in onMessage
    await app.question_anwsering(message.content, False)
  File "/rag-app/app.py", line 367, in question_anwsering
    async for chunk in runnable.astream_log(
  File "/usr/local/lib/python3.11/site-packages/langchain_core/runnables/base.py", line 752, in astream_log
    await task
  File "/usr/local/lib/python3.11/asyncio/futures.py", line 290, in __await__
    return self.result()  # May raise too.
           ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/asyncio/futures.py", line 203, in result
    raise self._exception.with_traceback(self._exception_tb)
  File "/usr/local/lib/python3.11/asyncio/tasks.py", line 267, in __step
    result = coro.send(None)
             ^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/langchain_core/runnables/base.py", line 706, in consume_astream
    async for chunk in self.astream(input, config, **kwargs):
  File "/usr/local/lib/python3.11/site-packages/langchain_core/runnables/base.py", line 2158, in astream
    async for chunk in self.atransform(input_aiter(), config, **kwargs):
  File "/usr/local/lib/python3.11/site-packages/langchain_core/runnables/base.py", line 2141, in atransform
    async for chunk in self._atransform_stream_with_config(
  File "/usr/local/lib/python3.11/site-packages/langchain_core/runnables/base.py", line 1308, in _atransform_stream_with_config
    chunk: Output = await asyncio.create_task(  # type: ignore[call-arg]
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/asyncio/futures.py", line 287, in __await__
    yield self  # This tells Task to wait for completion.
    ^^^^^^^^^^
  File "/usr/local/lib/python3.11/asyncio/tasks.py", line 339, in __wakeup
    future.result()
  File "/usr/local/lib/python3.11/asyncio/futures.py", line 203, in result
    raise self._exception.with_traceback(self._exception_tb)
  File "/usr/local/lib/python3.11/asyncio/tasks.py", line 267, in __step
    result = coro.send(None)
             ^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/langchain_core/runnables/base.py", line 2111, in _atransform
    async for output in final_pipeline:
  File "/usr/local/lib/python3.11/site-packages/langchain_core/output_parsers/transform.py", line 60, in atransform
    async for chunk in self._atransform_stream_with_config(
  File "/usr/local/lib/python3.11/site-packages/langchain_core/runnables/base.py", line 1283, in _atransform_stream_with_config
    final_input: Optional[Input] = await py_anext(input_for_tracing, None)
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/langchain_core/utils/aiter.py", line 62, in anext_impl
    return await __anext__(iterator)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/langchain_core/utils/aiter.py", line 97, in tee_peer
    item = await iterator.__anext__()
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/langchain_core/runnables/base.py", line 806, in atransform
    async for output in self.astream(final, config, **kwargs):
  File "/usr/local/lib/python3.11/site-packages/langchain_core/language_models/chat_models.py", line 307, in astream
    raise e
  File "/usr/local/lib/python3.11/site-packages/langchain_core/language_models/chat_models.py", line 299, in astream
    assert generation is not None
           ^^^^^^^^^^^^^^^^^^^^^^
AssertionError

### Who can help?

_No response_

### Information

- [ ] The official example notebooks/scripts
- [ ] My own modified scripts

### Related Components

- [X] LLMs/Chat Models
- [X] Embedding Models
- [X] Prompts / Prompt Templates / Prompt Selectors
- [ ] Output Parsers
- [ ] Document Loaders
- [ ] Vector Stores / Retrievers
- [X] Memory
- [ ] Agents / Agent Executors
- [ ] Tools / Toolkits
- [X] Chains
- [X] Callbacks/Tracing
- [X] Async

### Reproduction

This is a random occurrence. Maybe after I ask many questions
when it happen,   Only clear the memory can recover.

### Expected behavior

fix it