[InstCombine] Fix rare condition violation in canonicalizeClampLike

With a "ult x, 0", the fold in canonicalizeClampLike does not validate
with undef inputs. This condition will usually have been simplified
away, but we should ensure the code is correct in case.
https://alive2.llvm.org/ce/z/S8HQ6H vs https://alive2.llvm.org/ce/z/h2XBJ_

See: https://reviews.llvm.org/D108049