[gnome-shell] background: Fix a bug with empty animations

[Jasper St. Pierre <jstpierre src gnome org>]

commit 8edd7ad32e83698ac5703851947eecffd5b14c2d
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Thu Mar 14 17:06:17 2013 -0400

    background: Fix a bug with empty animations
    
    Arrays always evaluate to true, even empty arrays,
    so we need to check the length to make sure we have
    no files.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=695882

 js/ui/background.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/background.js b/js/ui/background.js
index e86dd6e..bfe06a5 100644
--- a/js/ui/background.js
+++ b/js/ui/background.js
@@ -387,7 +387,7 @@ const Background = new Lang.Class({
         this._animation.update(this._layoutManager.monitors[this._monitorIndex]);
         let files = this._animation.keyFrameFiles;
 
-        if (!files) {
+        if (files.length == 0) {
             this._setLoaded();
             this._queueUpdateAnimation();
             return;