title: Flutter: JSON Parsing data is null
body: <p>When I try to display the parsed JSON data in ListView, I am receiving this error:</p>
  
  <pre><code>'package:flutter/src/widgets/text.dart': Failed assertion: line 213 pos 15: 'data != null': is not true.
  </code></pre>
  
  <p>I checked the parsed data, and some fields are null. What is the proper way to check if the data is null and instead display string "Empty" ?</p>
  
  <pre><code>Results getShipment(int index) {
      return new Results(
        cargoTrackerCode: data[index]["cargoTrackerCode"]
       )
  }
  
  new Padding(                        
      child: new Text(widget.results.customerName,
          style: new TextStyle(
            fontSize: 18.0,
            color: Colors.white,
          )
      ),
  ),
  </code></pre>