LoopSink: Don't sink into blocks without an insertion point (PR38462)

In the PR, LoopSink was trying to sink into a catchswitch block, which
doesn't have a valid insertion point.

Differential Revision: https://reviews.llvm.org/D51307

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340900 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed