Mock Ajax Uncaught TypeError: Cannot read property 'toLowerCase' of undefined

Question

This is my AJAX :

    $('#FormPengeluaran').validate({
      submitHandler: function() {
        if (confirm("Are you sure you want to save?")) {
            var Data = $("#FormPengeluaran").serialize();
              $.ajax({
                type: "POST",
                url: "modules/Pengeluaran/RunSave.php",
                data: Data,
                global: false,
                success: function (result) {
                  //alert(result);
                  $('#information').html(result);
                }
              });
              return false;
            }
        }
    });

And I got Error From My Autocomplete

MOCK POST: modules/Pengeluaran/RunSave.php 

Object
jquery.autocomplete.init.js:24 
Uncaught TypeError: Cannot read property 'toLowerCase' of undefined
    at Object.response (jquery.autocomplete.init.js:24)
    at Object.<anonymous> (jquery.mockjax.js:153)
    at jquery.mockjax.js:189

When i input null URL no error found and nothing happens.

Ah i forgot to type my question, why my ajax going to mockjax ? mockjax what i have only for autocomplete not for submit, how to make my ajax didn't go to $.mockjax