title: EXTJS Store issue with Null Values -- useNull: doesn't have an affect --Help?
body: <p>Folks,</p>
  
  <p>I have a combobox component backed by a JSONStore.  The data loaded into the store is returning null for the combobox's value.  The value is an int.  The JSON decode process is converting the null value into a zero; causing the combobox to fail to render when it attempts to find the pk, zero that doesn't exist in its backing store.</p>
  
  <p>I've found the useNull: config option for data.Field objects, upgraded to 3.3.0 Final and set my int value for the combobox to useNull:true.  This isn't having any affect at all, unfortunately.  The decoded value is still being changed from null to zero.</p>
  
  <p>Any ideas about how to not set the field to a zero when the data for a JSON field is null?</p>
  
  <p>Here's a pic of what's going on.  Notice the data: value is zero, but the JSON value is null.</p>
  
  <p>Thanks! </p>
  
  <p>(gah!  stoopid reputation &lt; 10 so I can't directly post the pic.  View it here:  <a href="http://gordonjl.com/files/json_null_pic.png" rel="noreferrer">debug pic</a> )</p>
  
  <p>Also, here's my store's field config:</p>
  
  <pre><code>  fields: [
          {name:"id", type:"int"},
          {name:"occurenceDate", dateFormat: 'Y-m-d\\TH:i:s', type:"date"},
          {name:"docketNumber", type:"string"},
          {name:"courtLocationId", type:"int", useNull:true},
          {name:"assignedOfficerId", type:"int", useNull:true},
          {name:"primaryIncidentTypeId", type:"int", useNull:true},
          {name:"secondaryIncidentTypeId", type:"int", useNull:true},
          {name:"tertiaryIncidentTypeId", type:"int", useNull:true},
          {name:"incidentLocation", type:"string"},
          {name:"summary", type:"string"},
          {name:"personalItemsSeized", type:"string"},
          "supplements",
          "parties",
          "judgeIds"
      ]
  </code></pre>