[regression] After shrinking to zero size XCB window loses ability to future back surface reinitialisation

#include <QApplication>
#include <QWidget>
#include <QPainter>

class TestWidget : public QWidget
\{
public:
 TestWidget(QWidget *parent);
protected:
void paintEvent(QPaintEvent *ev);
};

TestWidget::TestWidget(QWidget *parent) :QWidget(parent)
\{
 setWindowFlags(Qt::Window);
}

void
TestWidget::paintEvent(QPaintEvent *ev)
\{
 QPainter P;
 int res=P.begin(this);
 Q_ASSERT(res);
}

static TestWidget *test_widget;

void test()
\{
 test_widget->resize(50, 100);
}

class MainWidget : public QWidget
\{
public:
 MainWidget():QWidget(0)
 \{

 }
protected:
 bool event(QEvent *ev)
 \{
  QEvent::Type type=ev->type();
  switch(type)
  \{
   case QEvent::MouseButtonPress:
   test();
   return 1;
  }
  return QWidget::event(ev);
 }
};

int main(int argc, char *argv[])
\{
 QApplication app(argc, argv);
 MainWidget widget;
 test_widget=new TestWidget(&widget);
 test_widget->show();
 test_widget->move(100, 100);
 test_widget->resize(0, 0);

 widget.resize(640, 256);
 widget.show();
 return app.exec();
}