Ok, for some reason I was under the impression that SCIStudio didn't even allow you to do this (I thought it only allowed integers for defines), but I guess I was wrong.
I could fix the crash pretty easily, but offering that functionality is a bit of work, and I don't want to risk de-stabilizing the version that's out there now. So I think I'd like to address this in the next version.
So for now, can you just work around it by specifying 1?
I really appreciate you finding these issues though!