Attempt to fix AccessibilityLocationChangesReceived crash.

This crash is happening in GetTreeFromId when tree_infos_ does not
contain the tree_id, which should not happen unless the tree
has recently been destroyed and AccessibilityLocationChangesReceived
is triggered immediately after.

The test was able to repro the crash stacktrace but this is difficult to
repro in a live build.

Bug: 405948702
Fixed: 376211390
Change-Id: I750fdd22854d641525b81124675e60bd716fa19c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6409711
Reviewed-by: Kristi Saney <kristislee@google.com>
Commit-Queue: Lauren Winston <lwinston@google.com>
Cr-Commit-Position: refs/heads/main@{#1439626}