title: How change the background color for a blank cell in QTableWidget
body: <p>If a cell have some data, using</p>
  
  <pre><code>tableWidget-&gt;item(8,0)-&gt;setBackgroundColor(Qt::red);
  </code></pre>
  
  <p>to change the background color will work, but if a cell is blank it will fail.</p>