Fix null pointer exception

Fix null pointer exception when SubscriptionManager.getSubId() returns
null to verify the result before accessing the first item.

Bug: 120649066
Test: Verified compilation and tested on device.
Change-Id: I4d36837ac58fdb7beb7eeaef0c2f967c3c4676bd
Merged-In: I5ed2dc7f0da3611f502d602d15b3b3d1a7ccddcb
1 file changed