// replace if ( typeof window.FormData !== 'function' ) {
if ( typeof window.FormData === undefined ) {

// before $.ajax send submit
$('input[type=file]',$form).each(function() {
      var files = $(this).prop('files');
      if ( files != undefined && files.length <= 0 ) {
          formData.delete($(this).attr('name'));
      }
});