'else' was missing in coverage range, resulting in odd looking reports

R=jgruber@chromium.org

Bug: v8:7179
Change-Id: I377cc557d51075256da27febdc8ab5442ea04d27
Reviewed-on: https://chromium-review.googlesource.com/816736Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50030}