Found while testing with asan.

Change-Id: I82529422770653535aae148a4acc6089c5a4fee7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1844786Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Martyn Capewell <martyn.capewell@arm.com>
Cr-Commit-Position: refs/heads/master@{#64136}