[BUG] None check is not there for FinalOutput.output

[bacharSalleh]

Describe the bug
Missing None check for el.output when validating final answer. The code checks isinstance(el, FinalOutput) but doesn't verify that el.output is not None before attempting to validate the final answer, which can cause False finalizing.

Expected behavior
The code should check if el.output is not None before attempting to use it:

 if self.final_answer_checks and el.output is not None:
    self._validate_final_answer(final_answer)

Existing Code

smolagents/src/smolagents/agents.py

Line 513 in 7113cf6

if self.final_answer_checks:

One more thing
I think yield ing FinalOutput when output is None (which happens when is_final_answer is False) is somehow not correct in terms of typing.

Packages version:

smolagents==1.18.0

[albertvillanova]

Thanks for reporting, @bacharSalleh.

Yes, I think the bug was introduced by:

• Agent.run() can return RunResult object #1337

Before it was:

if final_answer is not None and self.final_answer_checks:
    self._validate_final_answer(final_answer)

Now it is:

if isinstance(el, FinalOutput):
    final_answer = el.output
    if self.final_answer_checks:
        self._validate_final_answer(final_answer)

• This calls self._validate_final_answer even if final_answer is None

[albertvillanova]

Related to #1440.
Fixed by #1448.

[bacharSalleh]

Thanks so much for handling this, @albertvillanova 💪