Use null-safe operator for character properties access

[herpaderpaldent]

Refactored character property access to use the null-safe operator (?->) for corporation_id and alliance_id. This ensures that the code handles cases where the character object may be null, improving overall robustness and preventing potential errors.

This addresses #665

[what-the-diff]

PR Summary

• Improved Character Property Access
  The code has been improved to handle cases where some properties of the character might not exist. It now uses a null coalescing operator (?->), which makes it safer and less prone to errors. Specifically, this change has been applied for both corporation_id and alliance_id in the CharacterBatchJob.php file.

[qlty-cloud-legacy]

Code Climate has analyzed commit 3f6739c and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 89.9% (0.0% change).

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