searchbar: don't crash if track doesn't have artist/album set

https://bugzilla.gnome.org/show_bug.cgi?id=726721
simplify set_view_filter: don't re-read media's artist and album

https://bugzilla.gnome.org/show_bug.cgi?id=726721
mrpis: don't crash if some field cannot be found
mpris: don't crash if some field is missing and check other options if possible

https://bugzilla.gnome.org/show_bug.cgi?id=726721
mpris: skip all the exception when fetching track info

https://bugzilla.gnome.org/show_bug.cgi?id=726721
player: mpris: skip all the exception when getting artist