Attempting to undo from a previously non-existent cube is impossible

[NotStirred]

For example:
/mawm moveregen 0 32 0, move to some location where no cube exists at that position
/mawm undo

Source location is undone properly, but there is no previous packup to pull data from so the destination location cannot be reverted to it.

Possible solution: Wait for PR to add non-existent cube functionality, and remove the cubes in that area (regen)