Django jquery datatable: Uncaught TypeError: Cannot read property 'length' of undefined

brk

I'm trying to load data to jquery datatable from server in django 1.8.1. At the end of the process I'm getting "Uncaught TypeError: Cannot read property 'length' of undefined" javascript error.

View;

datas = Datas.objects.all()
jsonData = serializers.serialize('json', datas)
return HttpResponse(jsonData, content_type='application/json')

In the "Network" of browser it is seen that it returns json array like this;

[{"fields": {"objectname": "O1"}, "model": "my_app.datas", "pk": 1}]

Html;

<table class="table table-striped table-bordered table-hover" id="id_dataTable" style="cursor: pointer;">
</table>

Js;

  $('#id_dataTable').dataTable({
        "sAjaxSource": '/getData/',
        "aoColumns": [
            {'mData': 'fields.objectname'}
        ],
        "aoColumnDefs": [
            {
                "aTargets": [0],
                "sTitle": "Object",
                "sClass": "align-center"
            }
        ],
        "bProcessing": true,
        "bServerSide": true,
        "bPaginate": false
    });

Can you help ? thank you