Add null pointer judgment processing to prevent restarting

When getDisplayArea() is not default display,there will be a null pointer situation,
to avoid this situation, a null pointer judgment has been added.

Bug:295103280
Test:Stability test

Change-Id: I46c1463bab7889ba0395c67b8bd1ffa1148326cf
Signed-off-by: HanWang <hanwang627@gmail.com>