Hopefully fixes #4191 in a good way

* Deleted recipient account meant that `requesting_pseud` was nil; we already have a `request_byline` method, so we're going to use that instead
* However, a gift can't have a nil pseud, so we're not going to create a new gift through this path anyway
https://code.google.com/p/otwarchive/issues/detail?id=4191