Refactored some code as well to avoid unneccesaary `undefined`
checks in `overlays`. To be exact created an action_overlay
object of type `Overlay` such that the `reset_state` is just
`action_overlay = undefined` and having attributes like `$element`
and `close_handler`.
This would ensure that if you have an `active_overlay`, there will
be a registered `close handler` attached to it without needing to
write additional checks for `close_handler` just to satisfy type
checker.