LiteLLM with Gemini token issue

[handrew]

Using Gemini with LiteLLM - I get the following error

  File "/Users/handrew/env/lib/python3.11/site-packages/agents/extensions/models/litellm_model.py", line 111, in get_response
    input_tokens_details=InputTokensDetails(
                         ^^^^^^^^^^^^^^^^^^^
  File "/Users/handrew/env/lib/python3.11/site-packages/pydantic/main.py", line 253, in __init__
    validated_self = self.__pydantic_validator__.validate_python(data, self_instance=self)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pydantic_core._pydantic_core.ValidationError: 1 validation error for InputTokensDetails
cached_tokens
  Input should be a valid integer [type=int_type, input_value=None, input_type=NoneType]

Issue is that getattr will return None if the attribute exists but is literally None. Just have to add "or 0".

I will write a PR.

[rm-openai]

thanks for fixing!