[clang] [LifetimeSafety] Fix crash on ternary operator when one of the expressions is `throw` (PR #190345)

[via cfe-commits]

NeKon69 wrote:

I guess I could just put `isInevitablySinking` in my code, and later create a follow up PR that will add caching to that function, I looked through it and it actually doesn't look that bad

https://github.com/llvm/llvm-project/pull/190345