QString::toUcs4() returns incorrect value

QString::toUcs4() returns incorrectly resized QVector against non-BMP characters.

The following code can be used to reproduce the issue

const uint kData[] = { 0x10000 };
QString test = QString::fromUcs4(kData, 1);
const QVector<uint> ucs4s = test.toUcs4();
if (ucs4s.size() == 1) {
    qDebug() << "correct";
} else {
    qDebug() << "wrong";
}

This was working correctly with Qt 4.7, it got broken with SHA 2916b0749902ee51a3deab982e53189e72c3b693