Faithfulness checker crashes when a context chunk has `text: None`

[Aburke225]

check() builds the context with chunk.get("text", ""), but when the key is present with value None, .get() returns None (the default applies only to missing keys), and the subsequent " ".join(...) raises TypeError.

Steps to reproduce:

from rag.evaluator.faithfulness_checker import FaithfulnessChecker
FaithfulnessChecker().check('Knows Python.', [{'text': None}])
# observed: TypeError: sequence item 0: expected str instance, NoneType found

Related failing test: test_none_context_chunk_text in tests/unit/test_faithfulness_checker.py.

[AdhravRai]

Hi, I will like to work on this issue.I checked the reproduction and the related test, and the fix looks fairly contained to the faithfulness checker and its test. I’ll take a look at how the existing code handles missing/empty context values and add the appropriate handling for "NOne".

[hadbiaghiles]

I'd like to take this. I'll look at how missing/empty context values are handled today and add proper handling when text is present but None, plus cover test_none_context_chunk_text.

[hadbiaghiles]

Opened a PR with the fix: #76