Toast: Fix ActivityRecord does not attached to process

ActivityRecord's IApplicationThread has been set to null due
to the process being killed. At this time, the ActivityRecord
is no longer used.

Bug: 249221879

Test: build and boot

Signed-off-by: hupeng3 <hp121520@gmail.com>
Change-Id: I47b8ee8cb779dc64c4353d39d38b6c5d65fb8373