Allow not setting a shortcut for controller

I have a controller with only 4 buttons. It is detected by Spice-Up, but it does not let me map the actions because I need 5 different buttons for it to let me.

For example, I would like to be able to set:

- Next Slide: Button 0
- Previous Slide: Button 1
- Set Jump: _Disabled_
- Jump to Slide: _Disabled_
- Toggle Presentation: Button 2