[clang] [clang] Fix null dereference on return in lambda attribute statement expr (PR #66643)

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cor3ntin wrote:

@Fznamznon I think so too, although I'd be inclined to move the test to `clang/test/Parser/` because even though the fix is in Sema, it's testing a wrong parse.

The commit message also could do with a longer description.

Otherwise LGTM

https://github.com/llvm/llvm-project/pull/66643