state is not restored correctly

CMakeLists.txt

project(testguiapp)
cmake_minimum_required(VERSION 2.6)
find_package(Qt4 REQUIRED)

include_directories(${QT_INCLUDES} ${CMAKE_CURRENT_BINARY_DIR})

set(testguiapp_SRCS testguiapp.cpp main.cpp)
qt4_automoc(${testguiapp_SRCS})
add_executable(testguiapp ${testguiapp_SRCS})
target_link_libraries(testguiapp ${QT_QTCORE_LIBRARY} ${QT_QTGUI_LIBRARY})

main.cpp

#include <QtGui/QApplication>
#include "testguiapp.h"


int main(int argc, char** argv)
{
    QApplication app(argc, argv);
    testguiapp foo;
    foo.show();
    return app.exec();
}

testguiapp.cpp

#include "testguiapp.h"

#include <QtGui/QLabel>
#include <QtGui/QMenu>
#include <QtGui/QMenuBar>
#include <QtGui/QAction>
#include <QDockWidget>
#include <QToolBar>
#include <QDebug>

testguiapp::testguiapp()
{
    resize(400, 500);
    QToolBar* toolbar = new QToolBar(this);
    toolbar->setObjectName("toolbar");
    QAction* a = new QAction(this);
    a->setText( "save" );
    connect(a, SIGNAL(triggered()), this, SLOT(save()));
    toolbar->addAction(a);

    a = new QAction(this);
    a->setText( "restore" );
    connect(a, SIGNAL(triggered()), this, SLOT(restore()));
    toolbar->addAction(a);
    addToolBar(toolbar);

    createGui();
}

testguiapp::~testguiapp()
{}

void testguiapp::save()
{
    qDebug() << "save";
    mState = saveState();
}

void testguiapp::createGui()
{
    mLabel = new QLabel(this);
    mLabel->setText("Hello World!");
    mLabel->setObjectName("mainwidget");
    setCentralWidget(mLabel);

    mLeftDock = new QDockWidget(this);
    mLeftDock->setObjectName("leftdock");
    QLabel* label = new QLabel(mLeftDock);
    label->setObjectName("labelDock");
    addDockWidget(Qt::RightDockWidgetArea, mLeftDock);
    mLeftDock->setWidget(label);
}

void testguiapp::deleteGui()
{
    delete mLabel;
    delete mLeftDock;
    mLabel = 0;
    mLeftDock = 0;
}

void testguiapp::restore()
{
    qDebug() << "restore";
    deleteGui();
    createGui();
    restoreState(mState);
}


#include "testguiapp.moc"

testguiapp.h

#ifndef testguiapp_H
#define testguiapp_H

#include <QtGui/QMainWindow>
#include <QLabel>
#include <QDockWidget>

class testguiapp : public QMainWindow
{
    Q_OBJECT

public:
    testguiapp();
    virtual ~testguiapp();

protected Q_SLOTS:
    void save();
    void restore();

protected:
    void createGui();
    void deleteGui();

private:
    QByteArray mState;
    QLabel* mLabel;
    QDockWidget* mLeftDock;
    QByteArray mWidgetState;
    QByteArray mCentralWidgetState;
};

#endif // testguiapp_H