Hey,
Washi, my colleague fixed the issue just replace
if(!empty($form_data['your-subscription'])) {
$user_helper = &WYSIJA::get('user','helper');
$user_helper->addSubscriber($list_data);
}
with
if( ! empty($form_data['your-subscription'][0]) ) {
$user_helper = &WYSIJA::get('user','helper');
$user_helper->addSubscriber($list_data);
}