title: Grid store config throws "Uncaught TypeError: Cannot read property 'buffered' of undefined"
body: <p>I have form and grid. the user must enter data in form fields then display related records in the grid. </p>
  
  <p>I want to implement a search form, e.g: user will type the name and gender of the student,
  then will get a grid of all students have the same name and gender.</p>
  
  <p>So, I use Ajax to send form fields value to PHP and then create a <code>json_encode</code> which will be used in grid store.</p>
  
  <p>I am really not sure if my idea is good. But I haven't found another way to do that.</p>
  
  <p>The problem is there is a mistake in my store but I couldn't figure out what it is. I get this error:
  <code>Uncaught TypeError: Cannot read property 'buffered' of undefined</code></p>
  
  <p><strong>My View:</strong></p>
  
  <pre><code>{
    xtype: 'panel',
    layout: "fit",
    id: 'searchResult',
    flex: 7,
    title: '&lt;div style="text-align:center;"/&gt;SearchResultGrid&lt;/div&gt;',
    items: [{
      xtype: 'gridpanel',
      store: 'advSearchStore',
      id: 'AdvSearch-grid',
      columns: [{
          xtype: 'gridcolumn',
          dataIndex: 'name',
          align: 'right',
          text: 'name'
        }, {
          xtype: 'gridcolumn',
          dataIndex: 'gender',
          align: 'right',
          text: 'gender'
        }
      ],
      viewConfig: {
        id: 'Arr',
        emptyText: 'noResult'
      },
      requires: ['MyApp.PrintSave_toolbar'],
      dockedItems: [{
        xtype: 'PrintSave_tb',
        dock: 'bottom',
      }]
    }]
  }
  </code></pre>
  
  <p><strong>My Controller:</strong></p>
  
  <pre><code>.
  .
  .
  xmlhttp.open("GET","AdvSearch.php?search_name="+search_name,true);
  xmlhttp.send(null); 
  </code></pre>
  
  <p><strong>My PHP script:</strong></p>
  
  <pre><code>if (!$con) {
      throw new Exception("Error in connection to DB");
  }
  
  $query ="SELECT name, gender FROM students  WHERE name ILIKE '%$search_name%' ";
  $result = pg_query($query); 
  
  while ($row = pg_fetch_array($result)) {
     $Arr[] = array('name' =&gt; $row[0], 'gender' =&gt; $row[1]);
  }
  
  $searchResult_list = array();
  $searchResult_list['success'] = true;
  $searchResult_list['Arr'] = $Arr;
  
  $searchResult_list['totalCount'] = count( $searchResult_list['Arr'] );
  
  echo json_encode($searchResult_list); 
  
  if (!$result) 
      die("Error in query: " . pg_last_error());
  
  pg_close($con);
  </code></pre>
  
  <p><strong>My Store, Model:</strong></p>
  
  <pre><code>Ext.define('AdvSearchPost', {
    extend: 'Ext.data.Model',
    proxy: {
      type: 'ajax',
      url: 'AdvSearch.php',
      reader: {
        type: 'json',
        root: 'Arr',
        totalProperty: 'totalCount'
      }
    },
    fields: [{
        name: 'name'
      }, {
        name: 'type_and_cargo'
      }
    ]
  });
  advSearchStore = Ext.create('Ext.data.Store', {
    pageSize: 10,
    model: 'AdvSearchPost'
  });
  </code></pre>