Ah, this is a curious bug. Workaround (at least here): Press Alt + Shift + C to set Alt + C (Shift is ignored since Alt + c and Alt + C are equivalent)
Great, it works.
I hoped there would be an easy solution for this. I was looking for some config files where I could possibly change it but couldn't find anything.
My problem is solved now, for the future it might be useful to just disable the cancel button and have 'Esc' cancel the action.
Ah, this is a curious bug. Workaround (at least here): Press Alt + Shift + C to set Alt + C (Shift is ignored since Alt + c and Alt + C are equivalent)