fix: correct falsy-value handling in list utility helpers

[rishi-jat]

Summary

Fix incorrect handling of falsy values in deep_set and set_or_pop in trestle/common/list_utils.py.

Issue

Both functions used truthiness checks (if value) which caused valid falsy values such as 0, False, empty strings, and empty collections to be treated as missing and removed from dictionaries.

Changes Made

• Replace truthiness checks with explicit value is not None comparisons.
• Update logic in:
  • deep_set
  • set_or_pop

Tests

Added tests to ensure falsy values are preserved while None still removes keys.

[rishi-jat]

/cc @degenaro

[Copilot]

Pull request overview

This PR fixes incorrect handling of falsy values in dictionary helpers so that valid values like 0, False, and '' are not treated as “missing” and removed.

Changes:

• Update deep_set to use value is not None (instead of truthiness) when deciding whether to set vs. pop.
• Update set_or_pop to use value is not None (instead of truthiness) when deciding whether to set vs. pop.

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[Copilot]

Tests cover deep_set for None, but not for newly supported falsy values (e.g., 0, False, '') nor for set_or_pop semantics. Adding assertions for these cases would prevent regressions and clarify the intended behavior for falsy values vs. empty containers.

Suggested change

	if value is not None or not pop_if_none:
	dic[path[-1]] = value
	else:
	dic.pop(path[-1], None)
	if pop_if_none:
	set_or_pop(dic, path[-1], value)
	else:
	dic[path[-1]] = value

[rishi-jat]

@vikas-agarwal76 please have a look. Thanks!