there is always an integration session, so remove the check

actionpack/lib/action_dispatch/testing/integration.rb

@@ -457,7 +457,6 @@ module ActionDispatch
       # Copy the instance variables from the current session instance into the
       # test instance.
       def copy_session_variables! #:nodoc:
-        return unless integration_session
         %w(controller response request).each do |var|
           instance_variable_set("@#{var}", @integration_session.__send__(var))
         end