Fix two NPEs in TelephonyConnection

1. A trinary condition was screwed up and not doing a null check
properly
2. Add a null check in refreshConferenceSupported

Change-Id: Ib0a0d6c19b5e473e7c3c5ab8d1148142ae677ffa
Fixes: 35380056
Fixes: 64734432
Test: manual
1 file changed