[clang-tools-extra] [clang-tidy] Fix for cppcoreguidelines-pro-type-union-access if memLoc is invalid (PR #104540)

[Julian Schmidt via cfe-commits]

https://github.com/5chmidti requested changes to this pull request.

This is still missing a release note, see https://github.com/llvm/llvm-project/blob/40975da950c95124155b752cd683d945f7d203fd/clang-tools-extra/docs/ReleaseNotes.rst?plain=1#L104 for where to add it and how they look like

Functionality-wise, this looks good

https://github.com/llvm/llvm-project/pull/104540