SizeGrip missing

#include <QLabel>
#include <QSizeGrip>
#include <QGridLayout>
MainWindow::MainWindow(QWidget *parent)
  : QMainWindow(parent)
{
  auto w = new QWidget;
  auto g = new QGridLayout( w );
  auto l = new QLabel( qVersion() );

  auto r = new QSizeGrip( this );
  r->setVisible( true );

  g->setMargin( 0 );
  g->addWidget( l, 0,0, 1,1 );
  g->addWidget( r, 1,1, 1,1 );

  setCentralWidget( w );
}