Instead of checking against some version of "isType()" go ahead and
use the conversion to bool to check if we've managed to get a type
that isn't default constructed - as we meant to in the first place.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186556 91177308-0d34-0410-b5e6-96231b3b80d8