fix(condition): assert_in/assert_not_in wrongly reject falsy values present in the list

[chuenchen309]

Bug

_assert_in/_assert_not_in short-circuit on if not value, but this checks the truthiness of the value being tested for membership, not whether it's absent. A falsy value that is legitimately present in the expected list (e.g. an empty string in a picklist that allows an empty option) is silently rejected by in and silently accepted by not in, before the actual membership check ever runs.

Every other comparator in this file (_assert_equal, _assert_greater_than, _assert_null, etc.) guards with if value is None, not if not value — _assert_in/_assert_not_in are the only outliers.

Fix

Match the file's own established pattern: guard on value is None instead of not value.

Tests

• New test test_process_conditions_in_matches_falsy_value_present_in_list (via the real ConditionProcessor.process_conditions path, matching this file's existing test style): red before the fix, green after.
• Full tests/utils/test_condition_processor.py (5 tests) + tests/nodes/if_else/ (24 tests, the node that consumes this processor) pass.
• Full test suite (604 tests) passes.
• ruff check / ruff format --check / ty check clean on the changed files.

AI disclosure

Found, reproduced, and fixed with AI assistance (Claude Code), which noticed the inconsistency by comparing _assert_in/_assert_not_in's guard against every other comparator function in the same file. I independently reproduced the pre-fix bug and the fix's correctness by running the tests directly before opening this PR.

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[chuenchen309]

I have read the CLA Document and I hereby sign the CLA