Update all calling methods of SessionApiClient::OnSessionValidate()

[Cekis]

This likely needs updating a bit deeper. It's being cast as a uint64 because the calling method has userData as a void * type. Because of 64 bits, a void * becomes a 64 bit value. The calling method needs to be updated to not accept a void if at all possible and all callers of the calling method should also be updated. Great catch!

Originally posted by @Cekis in #23 (comment)