[gnome-music] fix for undiscoverable urls.

[Vadim Rutkovsky <vrutkovsky src gnome org>]

commit 2fd334d78bcd1db1ed19c5566f9bf56e0079043a
Author: Sai <suman sai14 gmail com>
Date:   Tue Jul 16 19:56:50 2013 +0530

    fix for undiscoverable urls.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=704253

 src/widgets.js |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/widgets.js b/src/widgets.js
index 4109f07..4a07d88 100644
--- a/src/widgets.js
+++ b/src/widgets.js
@@ -252,7 +252,8 @@ const AlbumWidget = new Lang.Class({
                     let iter = this.model.append();
                     let escapedTitle = AlbumArtCache.getMediaTitle(track, true);
                     try{
-                        this.player.discoverer.discover_uri(track.get_url());
+                        if (track.get_url())
+                            this.player.discoverer.discover_uri(track.get_url());
                         this.model.set(iter,
                             [0, 1, 2, 3, 4, 5, 7, 9],
                             [ escapedTitle, "", "", "", this._symbolicIcon, track,  nowPlayingIconName, 
false]);