Failed to convert text into a Pydantic model due to error: 'NoneType' object has no attribute 'function_calling_llm'

Hi all, I am blocked with this error perhaps because of the following TODO: is there any ways you can help me getting unblocked? located at: site-packages/crewai/crew.py Line: 648

error:

```_execute_single_listener] Error in method write_chapters: Failed to convert text into a Pydantic model due to error: 'NoneType' object has no attribute 'function_calling_llm'

Traceback (most recent call last):

File "/Users/.... /src/write_a_book_with_flows/.venv/lib/python3.11/site-packages/crewai/utilities/converter.py", line 37, in to_pydantic

result = self.model.model_validate_json(response)

```

More context:

https://github.com/crewAIInc/crewAI-examples/tree/main/write_a_book_with_flows

```

for agent in self.agents:

agent.i18n = i18n

# type: ignore[attr-defined] # Argument 1 to "_interpolate_inputs" of "Crew" has incompatible type "dict[str, Any] | None"; expected "dict[str, Any]"

agent.crew = self # type: ignore[attr-defined]

agent.set_knowledge(crew_embedder=self.embedder)