[clang] Fix null-deref thanks to an attribute on a global declarator chunk (PR #83611)

[Erich Keane via cfe-commits]

erichkeane wrote:

Note to self when I get back to work:
1- Update commit message with bug #[ 83611](https://github.com/llvm/llvm-project/pull/83611)
2- Add bug # to release note.

https://github.com/llvm/llvm-project/pull/83611