Update app.py

app.py

@@ -1034,6 +1034,8 @@ def checkout():
             # Remove only the selected coupon
             updated_coupons = [coupon for coupon in existing_coupons if coupon.strip() != selected_coupon]
             updated_coupons_str = "\n".join(updated_coupons).strip()
+            if not updated_coupons:
+                updated_coupons_str = None  # Set to None if no coupons are left
 
             sf.Referral_Coupon__c.update(referral_coupon_id, {
                 "Coupon_Code__c": updated_coupons_str