title: empty TreeView in QML from jsonModel
body: <p>I am trying to display a Json TreeView in QML from c++ jsonModel (<a href="https://github.com/dridk/QJsonModel" rel="nofollow noreferrer">this one</a>) but it's displayed empty in QML, with no data in it. while running the example in c++ it works fine.I used TreeView as QML type and setContextProperty("qjsonmodel",model) in c++ to make the connection between c++ and QML.</p>
  
  <p>this is what's displayed in QML.</p>
  
  <p><img src="https://i.stack.imgur.com/Y54qM.png" alt=""></p>
  
  <pre><code>TreeView{
          id:tree
          x: 0
          //anchors.fill: parent
          width: 335
          height: 420
          anchors.topMargin: 0
          anchors.bottomMargin: 6
          anchors.rightMargin: 1287
          anchors.bottom: frame.top
          anchors.top: parent.top
          clip: true
  
          model: qjsonmodel
          TableViewColumn{
              title:"Defects"
  
          }
  
      }
  </code></pre>