Fix the issue that App crash on startForeground

Install single APP in any user space except Owner user, the APP
got crash when call startForeground in Service Component with
Notification which without SmallIcon.

External bug:https://code.google.com/p/android/issues/detail?id=209043


Internal bug: 28602381

Change-Id: I88a3b8afc213cafe0f280f9b44d6acd2ea0df207
Signed-off-by: Wang Le <wangle@xiaomi.com>