[gnome-shell] shellDBus: Fix error message returned from Eval

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

commit e12bf8daedacabcc8470a07682d1cbec08e1da6c
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Wed Nov 13 13:20:08 2013 -0500

    shellDBus: Fix error message returned from Eval
    
    Annoyingly, `message` on errors are non-enumerable, which mean that
    JSON.stringify on the error will produce `{}`. Just cast it to a string
    for now.

 js/ui/shellDBus.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/shellDBus.js b/js/ui/shellDBus.js
index 609b1c1..79ff46c 100644
--- a/js/ui/shellDBus.js
+++ b/js/ui/shellDBus.js
@@ -119,7 +119,7 @@ const GnomeShell = new Lang.Class({
                 returnValue = '';
             success = true;
         } catch (e) {
-            returnValue = JSON.stringify(e);
+            returnValue = '' + e;
             success = false;
         }
         return [success, returnValue];