Rails-facebooker2, current_facebook_user throw error when facebooks' user is logged in

Question

I am using facebooker2 in Rails 2.3.5 (ruby 1.8.6, and there's no possibility to upgrade its version), and the method current_facebook_user is throwing a error when the facebook's user is already logged in.

what i want to achieve is that the method current_facebook_user returns the facebook user's data when is logged in.

thanks in advance.