using null coalescing operator

src/iss-components/cart-dropdown/cart-dropdown.vue

@@ -252,7 +252,7 @@ export default {
                     result += sumTax(this.baseServiceLineItems);
                 } else {
                     // deductible-case need to show tax for Recycle Fee
-                    result += this.recycleFeeLineItem != null ? this.recycleFeeLineItem.salesTax : 0;
+                    result += this.recycleFeeLineItem?.salesTax ?? 0;
                 }
             }