QGraphicsScene::isActive() doesn't work correctly

#include <QtGui>

class BugReport : public QWidget
{
    Q_OBJECT

public:
    BugReport(QWidget *parent);
    void addTabs();

private:
    QTabWidget *m_pTabWidget;
    QGraphicsScene *m_pGraphicsScene;

private slots:
    void checkActive();
};

#include "main.h"

BugReport::BugReport(QWidget *parent) : QWidget(parent)
{
    QBoxLayout *pLayout = new QVBoxLayout;

    QPushButton *pButton = new QPushButton(tr("Check Active!"));
    connect(pButton, SIGNAL(clicked(bool)), SLOT(checkActive()));
    pLayout->addWidget(pButton);

    m_pTabWidget = new QTabWidget;
    pLayout->addWidget(m_pTabWidget);

    m_pGraphicsScene = new QGraphicsScene();

    setLayout(pLayout);
}

void BugReport::addTabs()
{
    m_pTabWidget->addTab(new QWidget(), "dummy");
    m_pTabWidget->addTab(new QGraphicsView(m_pGraphicsScene), "view");
}

void BugReport::checkActive()
{
    QMessageBox::information(this, tr("QGraphicsScene::isActive()"), tr("QGraphicsScene::isActive() = %1").arg(m_pGraphicsScene->isActive()));
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    BugReport bugReport(0);
    bugReport.show();
    bugReport.addTabs();
    return app.exec();
}