Silencing an MSVC warning about control reaching the end of a non-void function.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198804 91177308-0d34-0410-b5e6-96231b3b80d8
Attempting a fix the build bots should be happier with. Amends 198804.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198805 91177308-0d34-0410-b5e6-96231b3b80d8