[clang] [clang] fix sema init crash for not checking a ExprResult (PR #98102)

[Davide Italiano via cfe-commits]

dcci wrote:

> > > You should also add test coverage (clang/test/SemaCXX) for the changes and a release note (clang/docs/ReleaseNotes.rst).
> > 
> > 
> > @AaronBallman -- are you OK with a crash-on-invalid (the one in first post)? The original example we had crashed on valid code, but reducing a 35MB file with a lot of SFINAE is taking weeks with c-reduce. Thanks for your review :)
> 
> Ideally we'd have test coverage for both the crash-on-invalid and crash-on-valid code, if possible. If we can't get a reduction to a crash-on-valid case, then crash-on-invalid that also fixes the valid case would be okay. But we could perhaps help reduce the crash-on-valid code if you can share it.

Thank you Aaron. Unfortunately this is from some Meta internal codebase, so it's hard to share. I'm trying to reduce myself.

https://github.com/llvm/llvm-project/pull/98102