[clang] [clang][AST] fix dereference on class/struct layouts check. (PR #83686)

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Sirraide wrote:

> it seems [there is an ongoing fix](https://github.com/llvm/llvm-project/pull/83688), could you possibly try so we can just close this one.

Yeah, it seems that the pr I opened for #83684 also fixes both the reduced test cases for this issue (and it also doesn’t crash anymore if I try to compile the file that was linked in the issue), though it should be noted that that’s only after I noticed that there was another problem and fixed that too. 

I think we should be able to close this one, unless someone comes up with a test case that still crashes anyway.

https://github.com/llvm/llvm-project/pull/83686