Paint Sprite brush

I’ve just found that deleting a sprite from a Spritefile where it is being used as a sprite brush takes paint out. Oops.
Repeat by creating a new spritefile,with sprites A and B, assign B as a brush, paint into A, then delete B from the file.

Yes I tried that a little while ago and I think the tool just stopped having any effect, but maybe I was just lucky. It should probably just compare with the brush sprite when a deletion is about to happen, and if it was that one then revert back to the “circle” brush.