This was written before lazy feedback vectors and expects that the
feedback vector is always present. Instead just return undefined and
do nothing if there is no feedback vector.

Change-Id: I1ffddd672576cb794eda2d5922b574a8be65d579
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2007492Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65840}