in order to make it also work with optional registers.

Bug: v8:8562
Change-Id: Iaea905913cc9fd1637026b83e9356c740965e128
Reviewed-on: https://chromium-review.googlesource.com/c/1367807
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58105}