[clang] [clang][ObjC][CodeComplete] Fix crash on C-Style cast with parenthesized operand in ObjC++ (PR #180343)

[Oliver Hunt via cfe-commits]

https://github.com/ojhunt requested changes to this pull request.

I think you should move the validity check into CodeCompleteObjCInstanceMessage.

I wish we could make the test have a verifiable output, but after a bunch of attempts to thread the needle to get to the bad load that could produce a useful output I've given up.

https://github.com/llvm/llvm-project/pull/180343