Clearing the queue triggers a Application error

[kingosticks]

When we clear the queue we call resetSong() to clear the current song info by manually populating a fake Mopidy Tltrack object and passing it to setSongInfo(). We then end up trying to get images for the uri ' ' (a space character) which Mopidy doesn't like. Mopidy log available here.

{"message": "Application error", "code": 0, "data": {"message": "Expected a list of URIs, not u\' \'",

This is kind of related to #172