User objects seem to be treated as node objects resulting in errors

When registering as a new user I receive the following errors:

Notice: Undefined property: stdClass::$domains in expire_get_base_urls() (line 43 of C:\wamp\www\prima7\sites\all\modules\expire\expire.domain.inc).
Warning: Invalid argument supplied for foreach() in expire_get_base_urls() (line 43 of C:\wamp\www\prima7\sites\all\modules\expire\expire.domain.inc).
Notice: Undefined property: stdClass::$nid in expire_get_domains() (line 13 of C:\wamp\www\prima7\sites\all\modules\expire\expire.domain.inc).

In each of the above functions, it appears that the problem arises when the user object is treated like a node object. Didn't have a lot of time to look very deeply into it, though.