Add validation of null pointers for certain APIs Bug: angleproject:397315932 Change-Id: I1b4758e326efd2e28d5a4f589c7b156065594911 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6342394 Auto-Submit: Robic Sun <Robic.Sun@arm.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>