Clear fields that do not have metadata

Returning early when there is no metadata available means that fields
could potentially contain stale info, especially apparent in QQS. We
should be clearing those fields instead.

Fixes: 153606598
Test: manual - play from app with metadata, then switch to app without
(e.g. Recorder), observe QQS does not have first app's title showing

Change-Id: Ie280c10f67550ab0b3c680f72eeaef3f723ecb12