未捕获的TypeError：无法设置null数据表laravel的属性“data”

Question

i want to reload data in datatables after i delete it using ajax. i checked the database and the item was deleted,but datatables won't refresh and it returns this error

Uncaught TypeError: Cannot set property 'data' of null datatables laravel

also, i got this message from the alert

DataTables warning: table id=table1 - Invalid JSON response. For more information about this error, please see http://datatables.net/tn/1

this is the code :

jquery :

var tab= jQuery('#table1').DataTable({
    "columns": [
     null,
     null,
     null,
     { "width": "15%" }
   ]
  });

function getPageData() {
        jQuery.ajax({
            url: 'attend/f',
          type: 'GET',
          success: function(data){
             tab.ajax.reload();
        }
      });
    }

    jQuery(".btndelete").click(function(e){
      jQuery.ajaxSetup({
              headers: {
                  'X-CSRF-TOKEN': '{{ csrf_token() }}'
              }
          });
      var id= jQuery(this).data('id');
      e.preventDefault();
      swal({
        title: 'Are you sure?',
        text: "You won't be able to revert this!",
        type: 'warning',
        showCancelButton: true,
        confirmButtonColor: '#3085d6',
        cancelButtonColor: '#d33',
        confirmButtonText: 'Yes, delete it!'
      }).then(function () {

        jQuery.ajax({
          dataType: 'json',
          type: 'delete',
          url: 'attend/' + id + '/delete',
        }).done(function(data){
          getPageData();
        });

      })
    });

route :

public function attend1($id)
{
  $acara = \App\Model\MyEventList::where('id_user',$id)->get();
  return response()->json();
}