Uncaught TypeError: Cannot read property 'apply' of undefined

[sarvap-praharanayuthan]

Used along with Blueimp/Fileupload.

Code:

callbacks: {
     ajaxContentAdded:function () {
          setTimeout(function () {
               imageDropdown();
          },500);
     }
}

function imageDropdown() {
    $(".imagesListDropdown").chosen();
}

HTML part:

<select id="cover" class="imagesListDropdown form-control" required name="cover">
// populated with PHP from DB array
<?php echo "<option value='{$row['id']}' data-img-src='{$path}'>{$row['title']}</option>"; ?>
</select>

Resources loaded:
jQuery 2.1.0, Bootstrap 3.3.7.

[MaTToX3]

Any fix for that?