[clang-tools-extra] [clang-tidy] Avoid assert failure on non-identifier names in `readability-container-size-empty` (PR #181557)

[Baranov Victor via cfe-commits]

https://github.com/vbvictor approved this pull request.

LGTM, thank you!
Strangely, shouldn't we've hit this assert before? Release build must've silently suppressed it

https://github.com/llvm/llvm-project/pull/181557