Resize() is not similar to realloc() in that it allocates a new object
when passed a nullptr object.

Avoid corner cases around Resize(nullptr, size) where size may be
problematic if non-null by just requiring a valid object. The caller
can perform the necesary nullptr check.

Bug: chromium:1056170
Change-Id: Ic05972ae67c2968fc3eb002a6302b44e56b41ab4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2752147Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73336}