The comment was right but the actual condition wasn't. We should check
whether the value is _not_ loadable.

Bug: v8:7700
Change-Id: I1c721a56da5860c73c8179406abb1d3a8b9d08f6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3755111
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81638}