[gnome-shell] osdWindow: Fix setting a zero-level in osdWindow

[Bastien Nocera <hadess src gnome org>]

commit 2d18b06b3ff22e95869d2d4a647b6e229f499b65
Author: Bastien Nocera <hadess hadess net>
Date:   Fri Apr 25 15:14:22 2014 +0200

    osdWindow: Fix setting a zero-level in osdWindow
    
    Commit 7101cc3170bf727aebf918f37debff94ae705c85 caused a small
    regression insomuch that it checks for a valid "level" but simply using
    "if (level)" which will be false if level is undefined and if
    level == 0.
    
    Check for not undefined instead.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=727384

 js/ui/osdWindow.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/osdWindow.js b/js/ui/osdWindow.js
index 1916812..6263070 100644
--- a/js/ui/osdWindow.js
+++ b/js/ui/osdWindow.js
@@ -127,7 +127,7 @@ const OsdWindow = new Lang.Class({
 
     setLevel: function(level) {
         this._level.actor.visible = (level != undefined);
-        if (level) {
+        if (level != undefined) {
             if (this.actor.visible)
                 Tweener.addTween(this._level,
                                  { level: level,