OPP: Check whether notifier is intialized before cancelling notification

This change will check if notifier is intialized or not before
cancelling existing notifications. Sometimes notifier is not
initialized when OPP service is not started for the duplicate
Bluetooth process which could have been created during user switch
through ActivityManager.

Change-Id: I2ecd06b9729106e6137cdd3c7a6f77741c31b09e
CRs-Fixed: 2373783
1 file changed