``alias`` make decoding buggy

[calve]

Hi folks,

I noticed the following behaviour

> base32.decode(base32.encode("deadbeef111"))
< "d{adbe{f111"

which appers to be introduced by the alias behaviour. I nulled the aliases dictionnary to retablish the desired behaviour.

> base32.decode(base32.encode("deadbeef111"))
< "deadbeef111"