[InstCombine] fix crash while trying to narrow a binop of shuffles (PR40734)

https://bugs.llvm.org/show_bug.cgi?id=40734

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354144 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed