Thanks - this will be fixed on the next reboot.
From what I have seen, it's not abusable, but you can't use the slot for anything until you removed the item again (and it won't let you drag it out, because there are none of that item in the slot). So, to make your slot usable again, put at least one of that item in the slot, and then withdraw them again.
Anyhow, great catch. I completely missed that - while I did check for that on gold deposits, I forgot it for items. Well done.
