Out of bounds checks for LibraryPath

[IvoDD]

Reference Issues/PRs

What does this implement or fix?

We've encountered some fairly obscure arcticc folly::Range out of bounds failures. They are very unlikely but still can potentially cause surprising errors.

This pr fixes one and raises a more meaningful error for another

Any other comments?

Checklist

Checklist for code changes...

• [ ] Have you updated the relevant docstrings, documentation and copyright notice?
• [ ] Is this contribution tested against all ArcticDB's features?
• [ ] Do all exceptions introduced raise appropriate error messages?
• [ ] Are API changes highlighted in the PR description?
• [ ] Is the PR labelled as enhancement or bug so it appears in autogenerated release notes?