JSGrid Multiselect field

HTML

<link rel="stylesheet" href="http://js-grid.com/css/jsgrid.min.css">
<link rel="stylesheet" href="http://js-grid.com/css/jsgrid-theme.min.css">
<script src="http://js-grid.com/js/jsgrid.min.js"></script>
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1/themes/ui-lightness/jquery-ui.css">
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1/jquery-ui.min.js"></script>
<script src="http://www.erichynds.com/examples/jquery-ui-multiselect-widget/src/jquery.multiselect.js"></script>
<link rel="stylesheet" href="http://www.erichynds.com/examples/jquery-ui-multiselect-widget/jquery.multiselect.css">
<div id="jsGrid"></div>

CSS

html,
body {
    height: 100%;    
}

JavaScript

var db = {

    loadData: function(filter) {
        return $.grep(this.users, function(user) {
            return (!filter.Name || user.Name.indexOf(filter.Name) > -1);
        });
    },
    
    insertItem: function(item) {
        this.users.push(item);
    },
    
    deleteItem: function(item) {
        var index = $.inArray(item, this.users);
        this.users.splice(index, 1);
    }
    
};

window.db = db;

var countries = [
    {ID:1, Name: "USA" },
    {ID:2, Name: "Canada" },
    {ID:3, Name: "France" },
    {ID:4, Name: "UK" },
    {ID:5, Name: "Russia" }
];

db.users = [
    {
        "Account": "A758A693-0302-03D1-AE53-EEFE22855556",
        "Name": "Carson Kelley",
        "Country": [1, 2]
    },
    {
        "Account": "D89FF524-1233-0CE7-C9E1-56EFF017A321",
        "Name": "Prescott Griffin",
        "Country": [3]
    },
    {
        "Account": "06FAAD9A-5114-08F6-D60C-961B2528B4F0",
        "Name": "Amir Saunders",
        "Country": [4]
    },
    {
        "Account": "EED7653D-7DD9-A722-64A8-36A55ECDBE77",
        "Name": "Derek Thornton",
        "Country": [4]
    },
    {
        "Account": "2A2E6D40-FEBD-C643-A751-9AB4CAF1E2F6",
        "Name": "Fletcher Romero",
        "Country": [5]
    },
    {
        "Account": "3978F8FA-DFF0-DA0E-0A5D-EB9D281A3286",
        "Name": "Thaddeus Stein",
        "Country": []
    },
    {
        "Account": "658DBF5A-176E-569A-9273-74FB5F69FA42",
        "Name": "Nash Knapp",
        "Country": []
    }
];

var MultiselectField = function(config) {
    jsGrid.Field.call(this, config);
};

MultiselectField.prototype = new jsGrid.Field({
    
    items: [],
    textField: "",
    valueField: "",
    itemTemplate: function(Name) {
        return $.makeArray(Name).join(", ");
    },
    
    _createSelect: function(selected) { 
        var textField = this.textField;
        var valueField=this.valueField;
        var $result = $("<select>").prop("multiple", true);
        
        $.each(this.items,...