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

[Nicolas van Kempen via cfe-commits]

nicovank wrote:

There's a CI failure but looks unrelated. If you have a minute please rebase/merge main to trigger the checks again and hopefully the problem disappears. We can also just keep an eye on the buildbots post-merge tomorrow.

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