Feedback Random Brush permanently broken

I was messing around with the 2D extras package from here. Through a combination of clumsyness and misspelling, I set the random brush to pick randomly between some 5-digit large number of tiles.

This has permanently broken the random brush. If I select it, Unity hangs as it desperately tries to do... anything with those tiles. I can't figure out where the data about number of tiles selected is stored, so I don't seem to be able to fix it either.

Help?

 

Had to delete it from Library/GridBrush.