User registration: New user gets 404 on first login

When using the user registration module to invite a user, the use sometimes get a 404 on the first login. It is caused by an invalid URL:

http://localhost:8080/nuxeo/http://localhost:8080/nuxeo/nxpath/default/default-domain/workspaces/templateSamples@view_documents?language=fr_FR

I say "sometimes", because it seems that depending on the context, either the bug will occur, or the session will not be kept and the user will be redirected to his home page instead.

The bugs seems to be introduced by this commit:
https://github.com/nuxeo/nuxeo-platform-user-registration/commit/42564df99b687d6642556dc9322ddfbc0b9d81ed

In particular the line:

getContext().getRequest().getSession().setAttribute(
                START_PAGE_SAVE_KEY, redirectUrl);