Feature request: set a key to exit from a Check list without any selection

[marozsas]

I would like to have a way to exit from a check object pressing a exit key (ESC, "q", "x", whatever) returning a empty selection to the caller.

[bchao1]

You can do this by registering a new key handling operation. See here: https://github.com/bchao1/bullet/blob/master/DOCUMENTATION.md#topic_17