`user_signed_in?` throws when an invalid_token is passed

user_signed_in? calls Warden::Proxy#authenticate which ultimately calls Devise::Doorkeeper::Strategies::Doorkeeper#authenticate! which throws if a given token is invalid.

I believe the intent behind user_signed_in? and the Warden::Proxy#authenticate are to be passive auth checks and should not throw. I'm not sure if this is a problem with the implementation of the Strategy or with the implementation of Warden::Proxy#run_strategies_for. I notice that the Strategies wiki does not mention using throw :warden but the Failures wiki does. The documentation on Warden::Strategies::Base is ambigious.

See also wardencommunity/warden#203