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

[via cfe-commits]

zeyi2 wrote:

> Strangely, shouldn't we've hit this assert before? Release build must've silently suppressed it

It do seems weird... It is possible that we aren't using assertion builds for testing large codebases before.

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