preferences: No longer creates duplications.

ubiquity/chrome/content/preferences.xul

@@ -1,9 +1,8 @@
 <?xml version="1.0"?>
-<?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
 <window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-<script type="application/javascript;version=1.7">
+<script type="application/javascript;version=1.8">
 Components.utils.import("resource://ubiquity/modules/utils.js");
-Application.activeWindow.open(Utils.url("about:ubiquity")).focus();
-window.close();
+Utils.focusUrlInBrowser("about:ubiquity");
+close();
 </script>
 </window>