App should exit even when doing something long

[hasezoey]

Currently when i accidentally press "Backspace" again while i am in the music directory, it will try to search a way wider directory area and the process cannot be stopped with CTRL+C (or thereof) and needs to be killed (kill -9) because it takes so long.

in my opinion the UI should still respond to at least stop requests, maybe extend this to allow just stopping the search and go back the the last known path.

PS: it should also have some kind of indicator that it is doing something like a loading bar or some dialog