Checkout pane minor AJAX error

Problem on checkout page (address pane): if i click on "Select one", i got (approximatelly) this JS AJAX pop-up error as follows:

HTTP Code: 200
Path: /system/ajax
Text: OK
Fatal error: Call to a member function copyAddress() on a non-object in uc_addresses/uc_addresses.ubercart.inc on line 168

I believe the solution is obvious, but i can't find it or i'm blind... anyway the problem is with the -1 that's considered as address ID. JS should validate the select box (option) value and check if the value is bigger then 0; and the request only if "validation" pass. Also the PHP (server side) part should valid the ID.

I hope this is not duplicate; but i didn't find it anywhere reported.