Handle the undefined promiseOrCapability case in
RejectPromiseReactionJob and FulfillPromiseReactionJob.

Fixed: chromium:1046213
Change-Id: If6f51c28189a27476969c7b5b456741b5be829be
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2050399
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66248}