QSGOpaqueTextureMaterial::compare sometimes segfaults when using QQuickImageProvider which returns non-transparent pixmap

int QSGOpaqueTextureMaterial::compare(const QSGMaterial *o) const
{
    Q_ASSERT(o && type() == o->type());
    const QSGOpaqueTextureMaterial *other = static_cast<const QSGOpaqueTextureMaterial *>(o);
    if (int diff = m_texture->textureId() - other->texture()->textureId())
        return diff;
    return int(m_filtering) - int(other->m_filtering);
}

if (int diff = m_texture->textureId() - other->texture()->textureId())

QPixmap RoundedImageProvider::requestPixmap(const QString &id, QSize *size, const QSize &requestedSize)
{
    int width = 800;
    int height = 800;
    if (size)
        *size = QSize(width, height);
    QPixmap pixmap(requestedSize.width() > 0 ? requestedSize.width() : width,
                   requestedSize.height() > 0 ? requestedSize.height() : height);
    pixmap.fill(Qt::red);

    // Draw on pixmap here

    return pixmap;
}