PayPal: Fixed rare bug

Author: Michael-Herzog

src/Smartstore.Modules/Smartstore.PayPal/Client/PayPalHttpClient.cs

@@ -599,7 +599,7 @@ private async Task<List<PurchaseUnitItem>> GetPurchaseUnitItemsAsync(ShoppingCar
 
             foreach (var item in model.Items)
             {
-                var cartItem = cart.Items.Where(x => x.Item.ProductId == item.ProductId).FirstOrDefault();
+                var cartItem = cart.Items.FirstOrDefault(x => x.Item.Id == item.Id);
                 var taxRate = await _taxService.GetTaxRateAsync(cartItem.Item.Product);
                 var calculationContext = await _priceCalculationService.CreateCalculationContextAsync(cartItem, calculationOptions);
                 var (unitPrice, subtotal) = await _priceCalculationService.CalculateSubtotalAsync(calculationContext);