Fix a crash in the LL parser where it failed to validate that the pointer operand of a GEP was valid.

This manifested as an assertion failure in +Asserts builds, and a hard crash in -Asserts builds.  Found by fuzzing the LL parser.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230934 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed