Fix undefined discountPercentage by providing default value

Previously, the absence of a discountPercentage caused issues. The code now uses a default value of 0 to ensure stability and prevent potential errors when the discount is not set.

services/nginx/app/modules/economic/customers/economicCustomers.php

@@ -73,7 +73,7 @@ class economicCustomers extends economic_m
         $products = $this->getCustomerProducts($customer_number, 1)->collection;
         $discount = $this->getCustomerProductDiscount($customer_number, $products[0]->product->productNumber);
         // Since the discount is global, we only need to get the discount for one product
-        return $discount->discountPercentage;
+        return $discount->discountPercentage ?? 0;
     }
 
     public function getCustomerProducts(int $customer_number, int $limit = 10, int $page = 1): object