Do not assume that the MaybeHandle that is returned when fetching for a property
is valid and instead check for its contents. Treat an empty handle as not
finding the right property.

Bug: chromium:1002827
Change-Id: Iac158086ec5f66cd9602f4a73ae78de367dd3e77
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1796556
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63672}