Fix reader mode crash related to automotive toolbar

Fixed: 1448900, b/284360061
Change-Id: I300784a8109ca706b9b4d55f8615ebf49e5e00b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4569041


Commit-Queue: Geoff Huang <geoffhuang@google.com>
Reviewed-by: Theresa Sullivan <twellington@chromium.org>
Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1149448}