[gnome-shell] AuthPrompt: properly remove user widgets

[Owen Taylor <otaylor src gnome org>]

commit d8d046f2b3ed3d9ec3d46ac17cb185838dae8a28
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Thu Oct 9 12:05:11 2014 -0400

    AuthPrompt: properly remove user widgets
    
    When replacing a user widget, we need to destroy the child, not just
    unparent it, or it will leak.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=738256

 js/gdm/authPrompt.js |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/js/gdm/authPrompt.js b/js/gdm/authPrompt.js
index 4160a56..3b435de 100644
--- a/js/gdm/authPrompt.js
+++ b/js/gdm/authPrompt.js
@@ -419,11 +419,13 @@ const AuthPrompt = new Lang.Class({
     },
 
     setUser: function(user) {
+        let oldChild = this._userWell.get_child();
+        if (oldChild)
+            oldChild.destroy();
+
         if (user) {
             let userWidget = new UserWidget.UserWidget(user);
             this._userWell.set_child(userWidget.actor);
-        } else {
-            this._userWell.set_child(null);
         }
     },