fix: prevent runtime error by adding null check for reward in _getDiscountableOnOrder

static/src/overrides/models/loyalty.js

@@ -11,6 +11,9 @@ patch(PosOrder.prototype, {
      * Override to calculate discountable amount without tax for all reward types
      */
     _getDiscountableOnOrder(reward) {
+        if (!reward) {
+            return { discountable: 0, discountablePerTax: {} };
+        }
         let discountable = 0;
         const discountablePerTax = {};