undo / redo is broken completely

[KrabCode]

when debugPrint is true printStack() prints obviously bad things like:

validation failed: new index out of bounds (-1)
redo (-1) 0 / 3
(0) "not found"
 1  "not found"
 2  "not found"
 3  "not found"

Maybe fix this while implementing the ChangeStore from #161 as their scopes of interest are very similar