If you use empty-bin on a bag that contains a powder (like flour, dye or plaster) then the bag's contents will simply be destroyed since they seemingly cant exist outside of a bag..

This can be particularly nasty, if you happen to run the command on a stockpile (with -r), which contains barrels, which may contain bags, which may contain powders ;)

The command probably needs another guard parameter like the existing -l/--liquids (for liquids) to control what is effectively "destroying" any powder. Maybe -p/--powders ?