Follow-up fix to r348811 for null Errors (which is the case for end iterators)

Not sure how I missed that in my testing, but obvious enough - this
causes segfaults when attempting to dereference the Error in end
iterators.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348814 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed