Fix NPE in CallStats.

If the target phone account for a call is not known, an NPE will take
place.

Fixes: 372974241
Flag: com.android.server.telecom.flags.telecom_metrics_support
Test: This is a bugfix to correct an NPE in the setup path for a flag.
Change-Id: I60f2ecb3144ca1ccca1716d66eaaa74545491444
1 file changed