QuantityControl::getSummaryValue

static function getSummaryValue(string $type, $productId): ?float
{
	$result = null;
	if (
		isset(self::$values[$type][$productId])
		&& is_array(self::$values[$type][$productId])
	)
	{
		$result = (float)array_sum(self::$values[$type][$productId]);
	}

	return $result;
}