https://crrev.com/c/3218150 introduced a bug where we would create a
filler entry without updating the object start bitmap.

Bug: v8:12295
Change-Id: Ic39cea54d2e0e8297fe58eb1e5b22d787874c565
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3218066
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77370}