Got a bug report on the latest version of the game, 549.
http://puu.sh/nTAQ4/9b75f00aa5.jpg
It happened when I was closing the game to the main menu after trying to delete a building that my hearthlings wouldn’t delete. Not sure if it’s related, but hopefully you guys can find out.
Edit: Oh, the game crashed after this. I guess it can be moved to crash reports instead of bug reports.