[llvm] [IR] Don't skip `catchswitch` when calling `BB::getFirstNonPHIOrDbgOrAlloca()` (PR #136056)

[Tyler Lanphear via llvm-commits]

tylanphear wrote:

That was my first instinct, though I do wonder: should the condition be `It == BB->end() || !CheckForNonVecCallsInSameBlock(&*It, BB->getTerminator()` instead? I admit, I'm not following the logic in this function well.

Probably the other use of `getFirstNonPHIOrDbgOrAlloca()` further down in the same function needs to be guarded as well.

https://github.com/llvm/llvm-project/pull/136056