[gnome-shell] gdmUtil: Fix auth prompt drawing over user list

[Ray Strode <halfline src gnome org>]

commit 0f8718287afd74e10d03d79aa3a230a72350551e
Author: Ray Strode <rstrode redhat com>
Date:   Wed Jun 7 15:00:11 2017 -0400

    gdmUtil: Fix auth prompt drawing over user list
    
    If the user fails to enter their password then hits escape, we
    jump back to the user list, then ask again for a password in a
    garbled screen. this commit fixes that by skipping a retry if
    the operation is cancelled.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=784361

 js/gdm/util.js |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/js/gdm/util.js b/js/gdm/util.js
index 48d5cb1..83ad422 100644
--- a/js/gdm/util.js
+++ b/js/gdm/util.js
@@ -540,7 +540,8 @@ const ShellUserVerifier = new Lang.Class({
                 let signalId = this.connect('no-more-messages',
                                             Lang.bind(this, function() {
                                                 this.disconnect(signalId);
-                                                this._retry();
+                                                if (this._cancellable && !this._cancellable.is_cancelled())
+                                                    this._retry();
                                             }));
             }
         } else {