[clang-tools-extra] [clang-tidy] Fix crash and infinite loop on incomplete types (PR #219781)

[Purna Chandra via cfe-commits]

Purna-Chandra-4706 wrote:

> Please mention changes in Release Notes.

I'll update the Release Notes!

Before I push, one question: should I keep the new tests in separate files like they are in this current PR, or merge them into the existing test files?

https://github.com/llvm/llvm-project/pull/219781