[railroad-dev] I would like to copy a plone proxy

[JR Courtois]

The context:
I have a folder in which I collect some datas that I store using
railroad. I want to make different versions of this folder, so I am
copying the folder. I don't want to duplicate the data in Railroad, just
have two different proxys on the same object.

The error:
'NoneType' object has no attribute 'resource_url_for'

I also cut and paste the object, and there is no trouble.
I've seen that this was on the todo list and I wonder if this is a good
idea to have more than one proxy on the same resource ?