[Verifier] Don't abort on invalid cleanuprets

Code in visitEHPadPredecessors assume a little too much about the
validity of a cleanupret with an invalid cleanuppad operand.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@262364 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed