[gnome-shell] NotificationDaemon: don't fail if a tray icon has no WM_CLASS

[Giovanni Campagna <gcampagna src gnome org>]

commit 7ebb5c6a107a3eef926f6709b8c8bc5a528d49ea
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Mon Sep 10 15:43:24 2012 +0200

    NotificationDaemon: don't fail if a tray icon has no WM_CLASS
    
    If there is no WM_CLASS for a tray icon, it returns null, not the empty
    string. Detect that case without an exception.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=683724

 js/ui/notificationDaemon.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/notificationDaemon.js b/js/ui/notificationDaemon.js
index 5b41197..2e800b3 100644
--- a/js/ui/notificationDaemon.js
+++ b/js/ui/notificationDaemon.js
@@ -499,7 +499,7 @@ const NotificationDaemon = new Lang.Class({
     },
 
     _onTrayIconAdded: function(o, icon) {
-        let wmClass = icon.wm_class.toLowerCase();
+        let wmClass = icon.wm_class ? icon.wm_class.toLowerCase() : '';
         if (STANDARD_TRAY_ICON_IMPLEMENTATIONS[wmClass] !== undefined)
             return;