<?php

class A
{
    /**
     * @return array|null
     * @throws Exception
     */
    public function getTierPrices()
    {
        return random_int(0, 1) ? [] : null;
    }
}

class B
{
    public function getPrice(A $product): float
    {
        $tierPrices = $product->getTierPrices();
        if (!empty($tierPrices)) {
            foreach ($tierPrices as $tierPrice) {
                if ($tierPrice >= 0) {
                    return $tierPrice;
                }
            }
        }

        return 0.0;
    }
}