jquery - Uncaught Error: cannot call methods on dialog prior to initialization

When a user clicks on a link, I want to populate a modal dialog and show it.
So I am populating this model dialog with the response of a GET method, using AJAX, like the following:
HTML:

     <a data-rec="@Model.rec" data-seg="@Model.seg" data-det="@Model.seg" 
class="btn btn-default checkRulesLink">Check Rules</a>


        <div id="dialog-rules" title="Rules" class="dialog">


        </div>

Javascript:

        $("#dialog-rules").dialog({
            autoOpen: false,
            modal: true,
            title: "Details",
            buttons: {
                Close: function () {
                    $(this).dialog('close');
                }
            }
        });

        $(".checkRulesLink").click(function (e) {
            $("#dialog-rules").html("");
            e.preventDefault();
            var rec = $(this).data('rec');
            var seg = $(this).data('seg');
            var det = $(this).data('det');
            $.ajax({
                url: "/Booking/CheckRules?rec=" + rec + "&seg=" + seg + "&det=" + det,
                success: function (result) {
                    console.log(result);
                    $("#dialog-rules").html(result);
                    $("#dialog-rules").dialog("open");
                }
            });

        });

The ajax call works fine
But whenever i click on the link, i get this error :

Uncaught Error: cannot call methods on dialog prior to initialization; attempted to 
call method 'open'
    at Function.error (VM32 jquery-1.12.4.js:253)
    at HTMLDivElement.<anonymous> (VM33 jquery-ui.js:246)
    at Function.each (VM32 jquery-1.12.4.js:370)
    at jQuery.fn.init.each (VM32 jquery-1.12.4.js:137)
    at jQuery.fn.init.$.fn.(anonymous function) [as dialog] (https://code.jquery.com/
ui/1.12.1/jquery-ui.js:236:10)
    at Object.success (Flights:18216)
    at fire (VM32 jquery-1.12.4.js:3232)
    at Object.fireWith [as resolveWith] (VM32 jquery-1.12.4.js:3362)
    at done (VM32 jquery-1.12.4.js:9840)
    at XMLHttpRequest.callback (VM32 jquery-1.12.4.js:10311)
error @ VM32 jquery-1.12.4.js:253
(anonymous) @ VM33 jquery-ui.js:246
each @ VM32 jquery-1.12.4.js:370
each @ VM32 jquery-1.12.4.js:137
$.fn.(anonymous function) @ VM33 jquery-ui.js:236
success @ Flights:18216
fire @ VM32 jquery-1.12.4.js:3232
fireWith @ VM32 jquery-1.12.4.js:3362
done @ VM32 jquery-1.12.4.js:9840
callback @ VM32 jquery-1.12.4.js:10311
XMLHttpRequest.send (async)
send @ VM32 jquery-1.12.4.js:10254
ajax @ VM32 jquery-1.12.4.js:9738
(anonymous) @ Flights:18211
dispatch @ VM32 jquery-1.12.4.js:5226
elemData.handle @ VM32 jquery-1.12.4.js:4878
2VM95:46 Uncaught TypeError: jQuery.easing[jQuery.easing.def] is not a function
    at Object.swing (eval at <anonymous> (VM32 jquery-1.12.4.js:349), <anonymous>:46:42)
    at init.run (VM32 jquery-1.12.4.js:7402)
    at tick (VM32 jquery-1.12.4.js:7747)
    at jQuery.fx.tick (VM32 jquery-1.12.4.js:8069)
swing @ VM95:46
run @ VM32 jquery-1.12.4.js:7402
tick @ VM32 jquery-1.12.4.js:7747
jQuery.fx.tick @ VM32 jquery-1.12.4.js:8069
setInterval (async)
jQuery.fx.start @ VM32 jquery-1.12.4.js:8093
jQuery.fx.timer @ VM32 jquery-1.12.4.js:8083
Animation @ VM32 jquery-1.12.4.js:7823
doAnimation @ VM32 jquery-1.12.4.js:7926
dequeue @ VM32 jquery-1.12.4.js:4157
(anonymous) @ VM32 jquery-1.12.4.js:4201
each @ VM32 jquery-1.12.4.js:370
each @ VM32 jquery-1.12.4.js:137
queue @ VM32 jquery-1.12.4.js:4194
animate @ VM32 jquery-1.12.4.js:7937
jQuery.fn.(anonymous function) @ VM32 jquery-1.12.4.js:8053
(anonymous) @ VM83:24
fire @ VM32 jquery-1.12.4.js:3232
add @ VM32 jquery-1.12.4.js:3291
jQuery.fn.ready @ VM32 jquery-1.12.4.js:3542
(anonymous) @ VM83:1
(anonymous) @ VM32 jquery-1.12.4.js:349
globalEval @ VM32 jquery-1.12.4.js:350
text script @ VM32 jquery-1.12.4.js:10372
ajaxConvert @ VM32 jquery-1.12.4.js:9332
done @ VM32 jquery-1.12.4.js:9789
callback @ VM32 jquery-1.12.4.js:10311
send @ VM32 jquery-1.12.4.js:10321
ajax @ VM32 jquery-1.12.4.js:9738
jQuery._evalUrl @ VM32 jquery-1.12.4.js:9902
domManip @ VM32 jquery-1.12.4.js:6086
append @ VM32 jquery-1.12.4.js:6269
(anonymous) @ VM32 jquery-1.12.4.js:6375
access @ VM32 jquery-1.12.4.js:4399
html @ VM32 jquery-1.12.4.js:6338
success @ Flights:18215
fire @ VM32 jquery-1.12.4.js:3232
fireWith @ VM32 jquery-1.12.4.js:3362
done @ VM32 jquery-1.12.4.js:9840
callback @ VM32 jquery-1.12.4.js:10311
XMLHttpRequest.send (async)
send @ VM32 jquery-1.12.4.js:10254
ajax @ VM32 jquery-1.12.4.js:9738
(anonymous) @ Flights:18211
dispatch @ VM32 jquery-1.12.4.js:5226
elemData.handle @ VM32 jquery-1.12.4.js:4878
js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:95 You have included the Google Maps 
JavaScript API multiple times on this page. This may cause unexpected errors.
Hg @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:95
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:158
google.maps.Load @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:18
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:158
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:159
373VM95:46 Uncaught TypeError: jQuery.easing[jQuery.easing.def] is not a function
    at Object.swing (eval at <anonymous> (VM32 jquery-1.12.4.js:349), <anonymous>:46:42)
    at init.run (VM32 jquery-1.12.4.js:7402)
    at tick (VM32 jquery-1.12.4.js:7747)
    at jQuery.fx.tick (VM32 jquery-1.12.4.js:8069)
swing @ VM95:46
run @ VM32 jquery-1.12.4.js:7402
tick @ VM32 jquery-1.12.4.js:7747
jQuery.fx.tick @ VM32 jquery-1.12.4.js:8069
setInterval (async)
jQuery.fx.start @ VM32 jquery-1.12.4.js:8093
jQuery.fx.timer @ VM32 jquery-1.12.4.js:8083
Animation @ VM32 jquery-1.12.4.js:7823
doAnimation @ VM32 jquery-1.12.4.js:7926
dequeue @ VM32 jquery-1.12.4.js:4157
(anonymous) @ VM32 jquery-1.12.4.js:4201
each @ VM32 jquery-1.12.4.js:370
each @ VM32 jquery-1.12.4.js:137
queue @ VM32 jquery-1.12.4.js:4194
animate @ VM32 jquery-1.12.4.js:7937
jQuery.fn.(anonymous function) @ VM32 jquery-1.12.4.js:8053
(anonymous) @ VM83:24
fire @ VM32 jquery-1.12.4.js:3232
add @ VM32 jquery-1.12.4.js:3291
jQuery.fn.ready @ VM32 jquery-1.12.4.js:3542
(anonymous) @ VM83:1
(anonymous) @ VM32 jquery-1.12.4.js:349
globalEval @ VM32 jquery-1.12.4.js:350
text script @ VM32 jquery-1.12.4.js:10372
ajaxConvert @ VM32 jquery-1.12.4.js:9332
done @ VM32 jquery-1.12.4.js:9789
callback @ VM32 jquery-1.12.4.js:10311
send @ VM32 jquery-1.12.4.js:10321
ajax @ VM32 jquery-1.12.4.js:9738
jQuery._evalUrl @ VM32 jquery-1.12.4.js:9902
domManip @ VM32 jquery-1.12.4.js:6086
append @ VM32 jquery-1.12.4.js:6269
(anonymous) @ VM32 jquery-1.12.4.js:6375
access @ VM32 jquery-1.12.4.js:4399
html @ VM32 jquery-1.12.4.js:6338
success @ Flights:18215
fire @ VM32 jquery-1.12.4.js:3232
fireWith @ VM32 jquery-1.12.4.js:3362
done @ VM32 jquery-1.12.4.js:9840
callback @ VM32 jquery-1.12.4.js:10311
XMLHttpRequest.send (async)
send @ VM32 jquery-1.12.4.js:10254
ajax @ VM32 jquery-1.12.4.js:9738
(anonymous) @ Flights:18211
dispatch @ VM32 jquery-1.12.4.js:5226
elemData.handle @ VM32 jquery-1.12.4.js:4878
maps.googleapis.com/maps/gen_204?target=api&ev=api_alreadyloaded&client=&key=AIzaSyASHc
SQGj-zxu3xPF5e07MFU4L_jxxBXcg&cad=src:apiv3,token:4u7gju54e3,ts:nhesob:1 GET http://
maps.googleapis.com/maps/gen_204?target=api&ev=api_alreadyloaded&client=&key=AIzaSyASHcSQGj
-zxu3xPF5e07MFU4L_jxxBXcg&cad=src:apiv3,token:4u7gju54e3,ts:nhesob 0 ()
Image (async)
LY.b @ stats.js:5
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:158
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:63
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:60
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:63
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:135
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:60
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:135
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:60
(anonymous) @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:135
Rd @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:63
Qd.va @ js?key=AIzaSyASHcSQGj-zxu3xPF5e07MFU4L_jxxBXcg:135
(anonymous) @ util.js:1
2334VM95:46 Uncaught TypeError: jQuery.easing[jQuery.easing.def] is not a function
    at Object.swing (eval at <anonymous> (VM32 jquery-1.12.4.js:349), <anonymous>:46:42)
    at init.run (VM32 jquery-1.12.4.js:7402)
    at tick (VM32 jquery-1.12.4.js:7747)
    at jQuery.fx.tick (VM32 jquery-1.12.4.js:8069)
swing @ VM95:46
run @ VM32 jquery-1.12.4.js:7402
tick @ VM32 jquery-1.12.4.js:7747
jQuery.fx.tick @ VM32 jquery-1.12.4.js:8069
setInterval (async)
jQuery.fx.start @ VM32 jquery-1.12.4.js:8093
jQuery.fx.timer @ VM32 jquery-1.12.4.js:8083
Animation @ VM32 jquery-1.12.4.js:7823
doAnimation @ VM32 jquery-1.12.4.js:7926
dequeue @ VM32 jquery-1.12.4.js:4157
(anonymous) @ VM32 jquery-1.12.4.js:4201
each @ VM32 jquery-1.12.4.js:370
each @ VM32 jquery-1.12.4.js:137
queue @ VM32 jquery-1.12.4.js:4194
animate @ VM32 jquery-1.12.4.js:7937
jQuery.fn.(anonymous function) @ VM32 jquery-1.12.4.js:8053
(anonymous) @ VM83:24
fire @ VM32 jquery-1.12.4.js:3232
add @ VM32 jquery-1.12.4.js:3291
jQuery.fn.ready @ VM32 jquery-1.12.4.js:3542
(anonymous) @ VM83:1
(anonymous) @ VM32 jquery-1.12.4.js:349
globalEval @ VM32 jquery-1.12.4.js:350
text script @ VM32 jquery-1.12.4.js:10372
ajaxConvert @ VM32 jquery-1.12.4.js:9332
done @ VM32 jquery-1.12.4.js:9789
callback @ VM32 jquery-1.12.4.js:10311
send @ VM32 jquery-1.12.4.js:10321
ajax @ VM32 jquery-1.12.4.js:9738
jQuery._evalUrl @ VM32 jquery-1.12.4.js:9902
domManip @ VM32 jquery-1.12.4.js:6086
append @ VM32 jquery-1.12.4.js:6269
(anonymous) @ VM32 jquery-1.12.4.js:6375
access @ VM32 jquery-1.12.4.js:4399
html @ VM32 jquery-1.12.4.js:6338
success @ Flights:18215
fire @ VM32 jquery-1.12.4.js:3232
fireWith @ VM32 jquery-1.12.4.js:3362
done @ VM32 jquery-1.12.4.js:9840
callback @ VM32 jquery-1.12.4.js:10311
XMLHttpRequest.send (async)
send @ VM32 jquery-1.12.4.js:10254
ajax @ VM32 jquery-1.12.4.js:9738
(anonymous) @ Flights:18211
dispatch @ VM32 jquery-1.12.4.js:5226
elemData.handle @ VM32 jquery-1.12.4.js:4878

Why is this happening and how can i fix it?
Any help would be appreciated


from jquery - Uncaught Error: cannot call methods on dialog prior to initialization