telecom: fix ringtone NPE when profile is set to silent

If ringmode is set to SUPPRESS ringtone manager returns a null ringtone.
Note: to repro exception set profile to silent, then configure, click
on phone app group, and set ring mode to "off"

Change-Id: Iaa80a628d9d80f1741d5a4c736a34e0cbbe00685
Merge branch 'remote' into mkl