jquery autocomplete - hide suggestion when no match is found

does anyone know how to hide the suggest开发者_如何学JAVAion list when no match is found . I am using jquery autocomplete from http://docs.jquery.com/UI/Autocomplete .

currently , the jquery shows all the result (or the first 20 ) when no match is found . but it should be empty in such a case.

my code is like this:

jQuery("#keyword").autocomplete('index.php', {
            width: keyword_width,
            multiple: true,
            selectFirst: false,
            minChars: 0,
            matchContains: false,
            multipleSeparator: " ",
            mustMatch: true,
            delay: 0
        });

does anyone have any suggestion how to do it?