JQUI AUTOCOMPLETE NO RESULTS MESSAGE EVENT USING 'RESPONSE'

HTML

<script src="http://code.jquery.com/ui/1.9.0/jquery-ui.js"></script>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.9.0/themes/base/jquery-ui.css">
<input />
<p id="empty-message"></p>

CSS

#empty-message { float: left; }
input { float: left }

JavaScript

$(function() {
    $("input").autocomplete({
        source: [
            "ActionScript",
            "AppleScript",
            "Asp",
            "BASIC",
            "C",
            "C++",
            "Clojure",
            "COBOL",
            "ColdFusion",
            "Erlang",
            "Fortran",
            "Groovy",
            "Haskell",
            "Java",
            "JavaScript",
            "Lisp",
            "Perl",
            "PHP",
            "Python",
            "Ruby",
            "Scala",
            "Scheme"
            ],
        response: function(event, ui) {
            if (ui.content.length === 0) {
                $("#empty-message").empty();
            } else {
                $("#empty-message").empty();
            }
        }
    });
});