Hide 'sip account' heading if there are no sip accounts.

Right now on the SIP settings menu, this is alway shown, even if
there's nothing listed below. Was a little visually confusing to me.
Now it will only show if there's at least one account listed.

There's still always an "add account" button at the top.

Bug: 17179743
Change-Id: Icd64f5c1f135d7341405ae4285a7697563331cdb
2 files changed