QT 5.3.2 QCoreApplication::postEvent: Unexpected null receiver- Conflicting properties 'visible' and 'visibility' error

[andykarp]

Upon running my QT application, I am seeing this Unexpected null receiver error. What is this error?

QCoreApplication::postEvent: Unexpected null receiver
file:///home/andy/Qt/5.3/gcc_64/qml/QtQuick/Controls/ApplicationWindow.qml: Conflicting properties 'visible' and 'visibility' for Window 'root'

The error also mentions something about conflicting 'visible' and 'visibility' properties in ApplicationWindow.qml

[andykarp]

I wanted to copy the contents of qquickwindowmodule.cpp (located in /home/andy/Qt/5.3/Src/qtdeclarative/src/quick/items/qquickwindowmodule.cpp) which contains the error message. I can't figure out why is the error message popping up when I run the application.
....
/****************************************************
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qquickwindowmodule_p.h"
#include "qquickscreen_p.h"
#include "qquickview_p.h"
#include <QtQuick/QQuickWindow>
#include <QtCore/QCoreApplication>
#include <QtQml/QQmlEngine>

#include <private/qguiapplication_p.h>
#include <private/qqmlengine_p.h>
#include <qpa/qplatformintegration.h>

QT_BEGIN_NAMESPACE

class QQuickWindowQmlImpl : public QQuickWindow, public QQmlParserStatus
{
Q_INTERFACES(QQmlParserStatus)
Q_OBJECT

Q_PROPERTY(bool visible READ isVisible WRITE setVisible NOTIFY visibleChanged)
Q_PROPERTY(Visibility visibility READ visibility WRITE setVisibility NOTIFY visibilityChanged)

public:
QQuickWindowQmlImpl(QWindow *parent = 0)
: QQuickWindow(parent)
, m_complete(false)
, m_visible(isVisible())
, m_visibility(AutomaticVisibility)
{
connect(this, &QWindow::visibleChanged, this, &QQuickWindowQmlImpl::visibleChanged);
connect(this, &QWindow::visibilityChanged, this, &QQuickWindowQmlImpl::visibilityChanged);
}

void setVisible(bool visible) {
    if (!m_complete)
        m_visible = visible;
    else if (!transientParent() || transientParent()->isVisible())
        QQuickWindow::setVisible(visible);
}

void setVisibility(Visibility visibility)
{
    if (!m_complete)
        m_visibility = visibility;
    else
        QQuickWindow::setVisibility(visibility);
}

Q_SIGNALS:
void visibleChanged(bool arg);
void visibilityChanged(QWindow::Visibility visibility);

protected:
void classBegin() {
QQmlEngine* e = qmlEngine(this);
//Give QQuickView behavior when created from QML with QQmlApplicationEngine
if (QCoreApplication::instance()->property("__qml_using_qqmlapplicationengine") == QVariant(true)) {
if (e && !e->incubationController())
e->setIncubationController(incubationController());
}
Q_ASSERT(e);
{
QV4::ExecutionEngine *v4 = QQmlEnginePrivate::getV4Engine(e);
QV4::Scope scope(v4);
QV4::ScopedObject v(scope, new (v4->memoryManager) QQuickRootItemMarker(e, this));
rootItemMarker = v;
}
}

void componentComplete() {
    m_complete = true;
    if (transientParent() && !transientParent()->isVisible()) {
        connect(transientParent(), &QQuickWindow::visibleChanged, this,
                &QQuickWindowQmlImpl::setWindowVisibility, Qt::QueuedConnection);
    } else {
        setWindowVisibility();
    }
}

private Q_SLOTS:
void setWindowVisibility()
{
if (transientParent() && !transientParent()->isVisible())
return;

    if (sender()) {
        disconnect(transientParent(), &QWindow::visibleChanged, this,
                   &QQuickWindowQmlImpl::setWindowVisibility);
    }

    // We have deferred window creation until we have the full picture of what
    // the user wanted in terms of window state, geometry, visibility, etc.

    if ((m_visibility == Hidden && m_visible) || (m_visibility > AutomaticVisibility && !m_visible)) {
        QQmlData *data = QQmlData::get(this);
        Q_ASSERT(data && data->context);

        QQmlError error;
        error.setObject(this);

        const QQmlContextData* urlContext = data->context;
        while (urlContext && urlContext->url.isEmpty())
            urlContext = urlContext->parent;
        error.setUrl(urlContext ? urlContext->url : QUrl());

        QString objectId = data->context->findObjectId(this);
        if (!objectId.isEmpty())
            error.setDescription(QCoreApplication::translate("QQuickWindowQmlImpl",
                "Conflicting properties 'visible' and 'visibility' for Window '%1'").arg(objectId));
        else
            error.setDescription(QCoreApplication::translate("QQuickWindowQmlImpl",
                "Conflicting properties 'visible' and 'visibility'"));

        QQmlEnginePrivate::get(data->context->engine)->warning(error);
    }

    if (m_visibility == AutomaticVisibility) {
        setWindowState(QGuiApplicationPrivate::platformIntegration()->defaultWindowState(flags()));
        setVisible(m_visible);
    } else {
        setVisibility(m_visibility);
    }
}

private:
bool m_complete;
bool m_visible;
Visibility m_visibility;
QV4::PersistentValue rootItemMarker;
};

void QQuickWindowModule::defineModule()
{
const char uri[] = "QtQuick.Window";

qmlRegisterType<QQuickWindow>(uri, 2, 0, "Window");
qmlRegisterRevision<QWindow,1>(uri, 2, 1);
qmlRegisterRevision<QWindow,2>(uri, 2, 2);
qmlRegisterRevision<QQuickWindow,1>(uri, 2, 1);//Type moved to a subclass, but also has new members
qmlRegisterRevision<QQuickWindow,2>(uri, 2, 2);
qmlRegisterType<QQuickWindowQmlImpl>(uri, 2, 1, "Window");
qmlRegisterUncreatableType<QQuickScreen>(uri, 2, 0, "Screen", QStringLiteral("Screen can only be used via the attached property."));

}

#include "qquickwindowmodule.moc"

QT_END_NAMESPACE

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