`allow_zero_lintable_files: true` doesn't work when added to a parent config that's loaded by a child config

New Issue Checklist

• I've Updated SwiftLint to the latest version.
• I've searched for existing GitHub issues.

Bug Description

Hi, allow_zero_lintable_files: true doesn't work when added to a parent config that's loaded by a child config.
It only works if allow_zero_lintable_files: true is specified in the child config.

$ swiftlint lint --config Foo/Bar/.swiftlint.yml --force-exclude --no-cache --quiet Foo/Bar/Tests/DeepLinkParserTests.swift
Error: No lintable files found at paths: 'Foo/Bar/Tests/DeepLinkParserTests.swift'

Environment

• SwiftLint version (run swiftlint version to be sure)
  0.61.0

• Xcode version (run xcodebuild -version to be sure)

Xcode 16.4
Build version 16F6

• Installation method used (Homebrew, CocoaPods, building from source, etc)
  Universal macOS Binary

• Configuration file:

# Foo/Bar/.swiftlint.yml

parent_config: ../../.swiftlint_base.yml

excluded:
  - Tests

# .swiftlint_base.yml

allow_zero_lintable_files: true

Reproduce the issue with swiftlint lint using Foo/Bar/.swiftlint.yml and the parent .swiftlint_base.yml shown in the report. Start at the configuration-loading and merging path for parent_config, then add a regression test covering allow_zero_lintable_files inherited from the parent. Done means the command no longer reports that no lintable files were found.