ASSERT: "!"No style available without QApplication!

Hello,

I am trying to learn QML and Qt i am trying to run one example but getting the below Error
ASSERT: "!"No style available without QApplication!"" in file kernel\qapplication.cpp, line 1123

My example code are below
piechart.h

Code:

---

#include <QtQuick/QQuickPaintedItem>
#include <QColor>
 
class piechart : public QQuickPaintedItem
{
    Q_OBJECT
    Q_PROPERTY(QString name READ name WRITE setName)
    Q_PROPERTY(QColor color READ color WRITE setColor)
public:
    piechart(QQuickItem *parent = 0);
    void paint(QPainter *painter);
};

---

piechart.cpp

Code:

---

#include "piechart.h"
 
piechart::piechart(QQuickItem *parent)
    : QQuickPaintedItem(parent)
{
 
}
 
void piechart::paint(QPainter *painter)
{
    QPen pen(m_color, 2);
    painter->setPen(pen);
    painter->setRenderHints(QPainter::Antialiasing, true);
    painter->drawPie(boundingRect().adjusted(1, 1, -1, -1), 90 * 16, 290 * 16);
}

---

main.cpp

Code:

---

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtQuick/QQuickView>
#include "piechart.h"
 
int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
 
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    return app.exec();
}

---

main.qml

Code:

---

import QtQuick 2.5
import QtQuick.Window 2.2
import QtCharts 2.0
 
Item {
    anchors.fill: parent
    property variant othersSlice: 0
 
    ChartView {
        id: chart
        title: "Top-5 car brand shares in Finland"
        anchors.fill: parent
        legend.alignment: Qt.AlignBottom
        antialiasing: true
 
        PieSeries {
            id: pieSeries
            PieSlice { label: "Volkswagen"; value: 13.5 }
            PieSlice { label: "Toyota"; value: 10.9 }
            PieSlice { label: "Ford"; value: 8.6 }
            PieSlice { label: "Skoda"; value: 8.2 }
            PieSlice { label: "Volvo"; value: 6.8 }
        }
    }
 
    Component.onCompleted: {
        // You can also manipulate slices dynamically
        othersSlice = pieSeries.append("Others", 52.0);
        pieSeries.find("Volkswagen").exploded = true;
    }
}

---

qmlApp.pro

Quote:

---

TEMPLATE = app

QT += core gui
QT += qml quick
CONFIG += c++11

SOURCES += main.cpp \
piechart.cpp

RESOURCES += qml.qrc

# Additional import path used to resolve QML modules in Qt Creator's code model
QML_IMPORT_PATH =

# Default rules for deployment.
include(deployment.pri)

HEADERS += \
piechart.h

---

Can anyone let me know why i am getting the Assert Error.