Check null for before using LockSettingsService

If the locksettings service fails to start, the resume on reboot
APIs will throw a nullptr exception in RecoverySystemService. Add
some check to prevent crashing the system server.

Bug: 184596745
Test: build
Change-Id: I5b1781612ec8d855d94b2828b5b5cfee9a84aebe
1 file changed