Avoid divide by zero for empty elements backing stores, and generally
don't account for empty_property_array / empty_fixed_array.

Bug: v8:7266
Change-Id: I5d1c5f43165810f7ec3bcebf3caf1bc737b46e59
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1559865
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60724}