[clang-tools-extra] [clang-tidy] Fix crash in modernize-use-designated-initializers check (PR #113688)

[Nicolas van Kempen via cfe-commits]

nicovank wrote:

I fixed a similar issue in 0aaac4fe194ae2249e1a01f9d6f5eac0d75c5bb2. There's an argument to be made whether this should be in the matchers (`isPOD`, `isAggregate` like here) versus an `hasDefinition` call in the parent before calling those matchers. I am slightly leaning towards the latter but this is not a strong opinion.

Add a small release notes entry?

https://github.com/llvm/llvm-project/pull/113688