[X86] Fix test checks script to handle run lines with no pipe checks

Fixes crashes in tests such as test/CodeGen/X86/masked_gather_scatter.ll which
contains a RUN: with no pipe chain.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286125 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed