refresh URL fragment when clearing the playlist

server/djrandom/frontend/static/js/djr/player.js

@@ -67,6 +67,8 @@ djr.Player.prototype.clearPlaylist = function() {
   this.playlist = new djr.Playlist();
   $('#playlistDiv').empty();
   djr.debug('new playlist: ' + this.playlist.uuid);
+  // Update the URL fragment.
+  djr.history.save(this.playlist.uuid);
 };
 
 // Merge all chunks into a single one.