Bluetooth Application Crash while try to pairing with laptop - IKDVXPSE-345

the handleRegistration will never run after we shutdown the handler thread first,
with this change, we can make sure the mObserver will never be null
when call handleRegistration.
bug:11148404

Change-Id: I93b351915b49cf59a7d2026b7d83a68a7e76dd38
1 file changed