Renderer sends empty xsesam:artist or xsesam:albumArtist

[phako]

If the DIDL-Lite parser finds artists on the item, (https://github.com/01org/dleyna-renderer/blob/master/libdleyna/renderer/device.c#L1448), it unconditionally creates the Variant for both xsesam:artist and xsesam:albumArtist, and will always send both over the bus, even if one is empty, e.g.

Nov 11 11:14:54 host dbus-monitor[1899]: dict entry(
Nov 11 11:14:54 host dbus-monitor[1899]: string "xesam:artist"
Nov 11 11:14:54 host dbus-monitor[1899]: variant                      array [
Nov 11 11:14:54 host dbus-monitor[1899]: string "Wir Sind Helden"
Nov 11 11:14:54 host dbus-monitor[1899]: ]
Nov 11 11:14:54 host dbus-monitor[1899]: )
Nov 11 11:14:54 host dbus-monitor[1899]: dict entry(
Nov 11 11:14:54 host dbus-monitor[1899]: string "xesam:albumArtist"
Nov 11 11:14:54 host dbus-monitor[1899]: variant                      array [
Nov 11 11:14:54 host dbus-monitor[1899]: ]
Nov 11 11:14:54 host dbus-monitor[1899]: )
Nov 11 11:14:54 host dbus-monitor[1899]: ]
Nov 11 11:14:54 host dbus-monitor[1899]: )