ExtJs store this.fields.get(field) is undefined

Here is simple example of store:

var cityStore = new Ext.data.JsonStore({
  url: '<%= ResolveUrl("~/json/Dictionaries/Cities.ashx")%>',
  //remoteSort: true,
  autoLoad: true
})

And here is responce from cities.ashx:

{
  "total": 34,
  "metaData": {
    "idProperty": "Id",
    "root": "data",
    "totalProperty": "total",
    "successProperty": "success",
    "messageProperty": "message",
    "sortInfo": "Id",
    "direction": "ASC",
    "fields": [
      {
        "name": "Id",
        "type": "number"
      },
      {
        "name": "Name",
        "type": "string"
      },
      {
        "name": "Count",
        "type": "number"
      }
    ]
  },
  "data": [
    {
      "Id": 5,
      "Name": "Винница",
      "Count": 0
    },
    {
      "Id": 30,
      "Name": "Горловка",
      "Count": 0
    },
    ...
  ],
  "success": true,
  "message": "ok"
}

If u will not add remoteSort:true u will get error:

this.fields.get(field) is undefined