Manages the close event for the current dialog.
        
        :param      event | <QCloseEvent>

def closeEvent( self, event ):
        """
        Manages the close event for the current dialog.
        
        :param      event | <QCloseEvent>
        """
        if ( XConfigDialog._instance == self ):
            XConfigDialog._instance = None
        
        super(XConfigDialog, self).closeEvent(event)