USPS error. Need help!

[josevi_camacho]

I'm having this error with guest costumers when they add an item to the cart.

 

Notice on line 1597 in file /home/tienda/public_html/modules/uspscarrier/uspscarrier.php
[8] Undefined index: iso_code

Notice on line 1598 in file /home/tienda/public_html/modules/uspscarrier/uspscarrier.php
[8] Undefined index: iso_code

[josevi_camacho]

Impossible to add the product to the cart.
textStatus: 'parsererror'
errorThrown: 'SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data'
responseText:

Notice: Undefined index: iso_code in /home/tienda/public_html/modules/uspscarrier/uspscarrier.php on line 1597

Notice: Undefined index: iso_code in /home/tienda/public_html/modules/uspscarrier/uspscarrier.php on line 1598

Notice: Undefined index: iso_code in /home/tienda/public_html/modules/uspscarrier/uspscarrier.php on line 1597

Notice: Undefined index: iso_code in /home/tienda/public_html/modules/uspscarrier/uspscarrier.php on line 1598
{"products":[{"id":43,"link":"http:\/\/tienda.uprrp.edu\/index.php?id_product=43&controller=product&id_lang=1","quantity":1,"image":"https:\/\/tienda.uprrp.edu\/img\/p\/7\/8\/78-home_default.jpg","image_cart":"https:\/\/tienda.uprrp.edu\/img\/p\/7\/8\/78-cart_default.jpg","priceByLine":"$8.99","name":"Gallito Black Cup","price":"$8.99","price_float":8.99,"idCombination":0,"idAddressDelivery":0,"is_gift":false,"hasAttributes":false,"hasCustomizedDatas":false,"customizedDatas":[]}],"discounts":[],"shippingCost":"$0.00","shippingCostFloat":0,"wrappingCost":"$0.00","nbTotalProducts":1,"total":"$8.99","productTotal":"$8.99","freeShipping":"$0.00","freeShippingFloat":0,"free_ship":false,"isVirtualCart":false,"hasError":false}