Moves the slide forward when clicked.
        
        :param      event | <QtCore.QMouseEvent>

def mouseReleaseEvent(self, event):
        """
        Moves the slide forward when clicked.
        
        :param      event | <QtCore.QMouseEvent>
        """
        if event.button() == QtCore.Qt.LeftButton:
            if event.modifiers() == QtCore.Qt.ControlModifier:
                self.goBack()
            else:
                self.goForward()
        
        super(XWalkthroughWidget, self).mouseReleaseEvent(event)