Avoid NullPointerException when activity is automatically recreated

Android system recreates activity with the saved Bundle object if it is
unexpectedly destroyed. If the death of the phone process caused such
unexpected destruction of activity, it is possible that StkAppService is
not started yet when the activity is recreated.

Bug: 31980334
Test: Confirmed NPE does not happen after the phone process is killed.

Change-Id: I7aeb570a6d866ec4ae6c33c7cea309bf83080d0a
3 files changed