Add proper Usage action handling to ensure proper help message

[0xcfff]

Without this change, todo.sh -h outputs empty line instead of plugin name in the list.

  Actions can be added and overridden using scripts in the actions
  directory.
  Add-on Actions:
    birdseye
    view

  See "help" for more details.

In the example above, there would be empty line instead of "view"