QUdpSocket: read access violation.

Offending code in QAbstractSocketPrivate::bind

• The socket engine gets set-up
• emits stateChanged(...) signal
• user code calls close() on the socket, enters QAbstractSocket::disconnectFromHost()
• following call to void QAbstractSocketPrivate::resetSocketLayer() deletes and NULL's the socketEngine
• bind function moves on in the code and uses socketEngine

emit q->stateChanged(state);
if (socketType == QAbstractSocket::UdpSocket)
        socketEngine->setReadNotificationEnabled(true);