handle NPE for findAppRequestInfoSmsIntentLocked

If this NPE happens on a binder thread (when onFilterComplete() is
called), it leaves the InboundSmsHandler state machine in a bad state as
the binder thread crashes and SMS_DELIVER intent is never broadcast. The
call flow is CarrierServicesSmsFilterCallback.onFilterComplete() ->
InboundSmsHandler.dispatchSmsDeliveryIntent() ->
AppSmsManager.handleSmsReceivedIntent() ->
AppSmsManager.findAppRequestInfoSmsIntentLocked()

Bug: 63797078
Bug: 65599291
Test: Manual
Change-Id: I06181f7ce30585d091f5ecedce8107cfc75d9dd2
(cherry picked from commit 226f2f36)