Recommit "[InstCombine] Expand `foldSelectICmpAndOr` ->...

Recommit "[InstCombine] Expand `foldSelectICmpAndOr` -> `foldSelectICmpAndBinOp` to work for more binops" (2nd Try)

Was missing a nullptr check before derefencing. Fixed + test case
included in the patch.

Re-Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D148414