[CGP] add another bailout for degenerate code (PR41064)

This is almost the same as:
rL355345
...and should prevent any potential crashing from examples like:
https://bugs.llvm.org/show_bug.cgi?id=41064
...although the bug was masked by:
rL355823
...and I'm not sure how to repro the problem after that change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356218 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed