[OPENMP] Fix for PR31417: assert failure when compiling trivial openmp

program

Offload related code is not quite ready yet, but some simple examples
must not crash the compiler. Patch fixes the problem in offloading code
with exceptions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290364 91177308-0d34-0410-b5e6-96231b3b80d8