Error occurred "`on_shutdown': wrong number of arguments"

[tana6]

Hello.

This issue has the same meaning as Issues #7.
It was displayed when the websocket's connection was disconnected.

`on_shutdown': wrong number of arguments (given 1, expected 0) (ArgumentError)

The current EventManager is as follows.

        def on_shutdown(event)
          @pinger.cancel if @pinger
          super
        end

I think that it is as follows.

        def on_shutdown(event)
          @pinger.cancel if @pinger
          super()
        end

By the way, I am using ruby 2.5.1.