undefined method `tr' for nil:NilClass

[jai-n]

I have debug the code and found this line give me error above
client = Mogli::Client.create_from_code_and_authenticator(data["code"], authenticator)
in following file

lib/facebooker2/rails/controller.rb

def oauth2_fetch_client_and_user_from_cookie
return unless fb_cookie?
sig,payload = fb_cookie.split('.')
return unless fb_signed_request_sig_valid?(sig, payload)
data = JSON.parse(base64_url_decode(payload))
authenticator = Mogli::Authenticator.new(Facebooker2.app_id, Facebooker2.secret, '')
client = Mogli::Client.create_from_code_and_authenticator(data["code"], authenticator)
user = Mogli::User.new(:id=>data["user_id"])
oauth2_store_client_and_user_in_session(client,user)
fb_sign_in_user_and_client(user, client)
end