日历不适用于jQuery 1.9.1(但它适用于jQuery 1.7.1）

我有以下脚本用于从下拉列表中选择日历日：

http://jsfiddle.net/nachosarmiento/XPj58/3/

$(document).ready(function () {
var calendario = new Date();
var una_noche = new Date();
var dos_noches = (new Date()).setDate(una_noche.getDate() + 1);
var tres_noches = (new Date()).setDate(una_noche.getDate() + 2);
var cuatro_noches = (new Date()).setDate(una_noche.getDate() + 3);
var cinco_noches = (new Date()).setDate(una_noche.getDate() + 4);
var atras = (new Date()).setDate(una_noche.getDate() - 1);
var dates;
var dates_in_string = '';
$('#simpliest-usage').multiDatesPicker({
    disabled: true,
    addDates: [una_noche]
});
$("#dias").on("change", function () {
    $('#simpliest-usage').multiDatesPicker('resetDates', 'picked');
    $('#simpliest-usage').multiDatesPicker('resetDates', 'disabled');

    if ($("#dias").val() == "1") {
        $('#simpliest-usage').multiDatesPicker({
            disabled: true,
            addDates: [una_noche]
        });
        dates = $('#simpliest-usage').multiDatesPicker('getDates');
        dates_in_string = '';
        for (var a in dates) dates_in_string += dates[a] + ' ';
        alert(dates_in_string);
    }
    if ($("#dias").val() == "2") {
        $('#simpliest-usage').multiDatesPicker({
            disabled: true,
            addDates: [una_noche, dos_noches]
        });
        dates = $('#simpliest-usage').multiDatesPicker('getDates');
        dates_in_string = '';
        for (var b in dates) dates_in_string += dates[b] + ' ';
        alert(dates_in_string);
    }
    if ($("#dias").val() == "3") {
        $('#simpliest-usage').multiDatesPicker({
            addDates: [una_noche, dos_noches, tres_noches],
            minDate: "una_noche"
        });
        dates = $('#simpliest-usage').multiDatesPicker('getDates');
        dates_in_string = '';
        for (var c in dates) dates_in_string += dates[c] + ' ';
        alert(dates_in_string);
    }
    if ($("#dias").val() == "4") {
        $('#simpliest-usage').multiDatesPicker({
            addDates: [una_noche, dos_noches, tres_noches, cuatro_noches],
            minDate: "una_noche"
        });
        dates = $('#simpliest-usage').multiDatesPicker('getDates');
        dates_in_string = '';
        for (var d in dates) dates_in_string += dates[d] + ' ';
        alert(dates_in_string);
    }
    if ($("#dias").val() == "5") {
        $('#simpliest-usage').multiDatesPicker({
            addDates: [una_noche, dos_noches, tres_noches, cuatro_noches, cinco_noches],
            minDate: "una_noche"
        });
        dates = $('#simpliest-usage').multiDatesPicker('getDates');
        dates_in_string = '';
        for (var e in dates) dates_in_string += dates[e] + ' ';
        alert(dates_in_string);
    }
});
});

它与jQuery 1.7.2完美配合，但是当我想使用jQuery 1.9.1时，它停止工作。

有人知道这个问题的原因吗？

PD：官方网站：http://multidatespickr.sourceforge.net/

谢谢。

问候。