Don't assume r.curApp is valid when finalizing broadcasts

There is an inherent race with process death such that r.curApp can wind
up null before we're trying to validate identity bookkeeping around
future broadcast policy.  Deal with this gracefully.

Bug: 160199815
Test: manual
Test: tests/ActivityTests
Change-Id: Ia6b2e973be64abb927838ad4b7d040b2f8839c71