GitLab

When a mini_view is removed, it outlives its desk, but ChromeVox
may try to get the accessible node data at this point when `desk_`
is nullptr.

BUG=999595
TEST=Manual

Change-Id: I62ebc62f4dee67e03da6fb5d588520451f9e85ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1779184Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692142}