title: Setting default for empty cell using jqxDropDownList
body: <p>I'm in the early days of using the jqxGrid. Everything has been going OK but now stuck on using a drop down list to select values for a cell. Here's the relevant code:</p>
  
  <pre><code>createeditor: function (row, column, editor) {
      var list = ['', 'x', '1', '2'];
      editor.jqxDropDownList({ autoDropDownHeight: true, source: list });
  }
  </code></pre>
  
  <p>What I was hoping would happen was that empty cells would be set to '' and then the prompt would never appear and a cell with a value in could be set to '', i.e. deleted. Instead the default prompt appears for an empty cell.</p>
  
  <p>I'd be grateful for any advice on how to get this to work.</p>
  
  <p>Thanks,</p>
  
  <p>Steph</p>