Fix standalone year-only copyright detection without holder

[dikshaa2909]

Fixes #4755

Summary

This PR fixes incorrect handling of standalone year-only copyright
detections during parse tree traversal.

Previously:

• Standalone year-only copyright statements (e.g., Copyright 2010)
  could pass through without proper holder validation.
• Author detections were yielded outside their intended conditional scope
  due to indentation and control-flow issues.

This caused inconsistent behavior in certain scan outputs.

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Changes Implemented

• Cleaned up parse tree traversal logic.
• Properly scoped yield author inside its include_authors condition.
• Ensured standalone year-only copyright detections are skipped when no holder is present.
• Maintained existing behavior for valid copyright + holder detections.
• No impact on unrelated components.

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Validation

• Full test suite executed locally.
• Failure count remains consistent with baseline (no new regressions introduced).
• Manual validation performed using d3 sample scan.
• Verified:
  • CHANGES.md does not produce unintended detections.
  • LICENSE detection remains correct.
  • No additional false positives introduced.

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Tasks

• Reviewed contribution guidelines
• PR is descriptively titled and links the original issue above
• Tests pass locally (no new failures introduced)
• Commits are in uniquely-named feature branch and has no merge conflicts
• Updated documentation pages (not applicable)
• Updated CHANGELOG.rst (not applicable)

Signed-off-by: Diksha Deware dikshadeware@gmail.com