Fix NPE in useCMap()

[LonelyMidoriya]

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of missing character map data by safely ignoring invalid inputs.
  • Added warning notifications when incomplete mapping information is encountered.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 432c82fd-d85a-4c25-a565-75556ff424b7

📥 Commits

Reviewing files that changed from the base of the PR and between 8a751e9 and 9a7b582.

📒 Files selected for processing (1)

• src/main/java/org/verapdf/pd/font/cmap/CMap.java

🚧 Files skipped from review as they are similar to previous changes (1)

• src/main/java/org/verapdf/pd/font/cmap/CMap.java

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📝 Walkthrough

Walkthrough

useCMap now validates its input. Null arguments produce a warning and no state change. Non-null arguments continue to merge mappings and codespaces.

Changes

CMap validation

Layer / File(s)	Summary
Guard null CMap inputs src/main/java/org/verapdf/pd/font/cmap/CMap.java	useCMap logs a warning and returns when the argument is null. Valid arguments retain the existing merge behavior.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: preventing a null-pointer exception in useCMap().
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch cmap-npe

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