fix: route unmatched when LLMMessagesRouter gets no reply text

[MohammadHijjawi97]

Related Issues

No existing issue. This PR includes a regression test for the crash.

Proposed Changes:

Proposed Changes:

LLMMessagesRouter indexed generator_result["replies"][0].text. Empty replies raised IndexError. A reply with text=None raised TypeError in re.search. Treat missing or non-string reply text as unmatched.

How did you test it?

Added unit tests for empty replies and None reply text.

Notes for the reviewer

Checklist

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• I have updated the related issue with new insights and changes.
• I have added unit tests and updated the docstrings.
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• I have documented my code.
• I have added a release note file, following the contributors guidelines.
• I have run pre-commit hooks and fixed any issue.

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