br_on_null should push a value on the stack, even in unreachable code.


Bug: v8:9495
Change-Id: Ic227c2f889b863a267a7ff5f33e539b43e66b42f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2567966Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71582}