fix: check if categories are empty, coupon is valid

src/QUI/ERP/Discount/Discount.php

@@ -389,6 +389,10 @@ public function canUsedWith(QUI\ERP\Products\Interfaces\ProductInterface $Produc
         }
 
         // category check
+        if (empty($categories)) {
+            return true;
+        }
+        
         foreach ($categories as $category) {
             $productCategories = $Product->getCategories();