Guard against NPE in VvmSimStateTracker

getTelephonyManager() with a PhoneAccountHandle is returning null on
some devices. This is a simple guard to unblock while waiting to get
a device for a full investigation.

Bug: 33945549
Change-Id: I36f5884654db36d8f0976980ec478c3d4ceacb47
Test: make. Cannot reproduce locally and pending full investigation.
1 file changed