Fix negative dim indexing

[MillaFleurs]

Proposed changes

Please include a description of the problem or feature this PR is addressing. If there is a corresponding issue, include the issue #.

array.h mixes signed and unsigned ints, causing potential issues #2993

Issue # 2993

Checklist

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• [ X] I have read the CONTRIBUTING document
• [ X] I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• [ X] I have added tests that prove my fix is effective or that my feature works
• [ N/A ] I have updated the necessary documentation (if needed)

[awni]

Thanks!