This is just adding an early exit, to avoid a big if-block spanning the
whole method.
Instead of doing this in the follow-up CL, which adds even more code to
that block, I pulled it out for easier review.

R=thibaudm@chromium.org

Bug: v8:11556
Change-Id: Ie4f2e0635fe9875c90d32be8224f1b0709c82e00
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2757687Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73405}