[clang] [Clang] Avoid crash when expression requirements are substitution failures (PR #176896)

[via cfe-commits]

GeneralK1ng wrote:

> thanks, this needs a release note. PLEASE add an entry to bug fixes to C++ support in release notes and link any issues you have fixed.

Thanks for the feedback!

I’ve added a release note entry under “Bug Fixes to C++ Support” and mirrored it in `ReleaseNotesTemplate.txt`

Please let me know if the release note wording or placement should be adjusted.

https://github.com/llvm/llvm-project/pull/176896