applets/mediacontroller: load album art on debut

This fixes the album art not being loaded when the applet is added to
the desktop.


(cherry picked from commit 72c66610)

applets/mediacontroller/contents/ui/CompactRepresentation.qml

@@ -102,6 +102,8 @@ MouseArea {
                         albumArt.loadAlbumArt();
                     }
                 }
+
+                Component.onCompleted: albumArt.loadAlbumArt()
             }
 
             ColumnLayout {