title: Qlabel settext is crashing
body: <p>I have created a dialog box using the qt designer. it generate me a .ui, cpp and header.</p>
  
  <p>the cpp is defined :</p>
  
  <pre><code>DialogAbout::DialogAbout(QWidget *parent) :
      QDialog(parent),
      ui(new Ui::DialogAbout)
  {
      ui-&gt;buildversion-&gt;setText("toto");
      ui-&gt;setupUi(this);
  }
  </code></pre>
  
  <p>header</p>
  
  <pre><code>class DialogAbout : public QDialog
  {
      Q_OBJECT
  
  public:
      explicit DialogAbout(QWidget *parent = 0);
      ~DialogAbout();
      QLabel *buildversion;
  
  private:
      Ui::DialogAbout *ui;
  };
  </code></pre>
  
  <p>and the UI looks like :</p>
  
  <p><img src="https://i.stack.imgur.com/20ipV.jpg" alt="enter image description here"></p>
  
  <p>My app is crashing each time I'm accessing the this dialog box when trying to </p>
  
  <pre><code>ui-&gt;buildversion-&gt;setText("toto");
  </code></pre>
  
  <p>Any idea ?</p>
  
  <p>Thanks</p>