title: QMessageBox::critical do not show title text
body: <p>I need to show simple error message</p>
  
  <pre><code>QMessageBox::critical(  nullptr, "My Title", "Text");
  </code></pre>
  
  <p>But the dialog appears with empty title.</p>
  
  <p>What I do wrong?</p>
  
  <p>PS: the OS: MacOS 10.9.1</p>