Used tools/armor are called null, best not to be sold.

Players are able to place a used tool (sword, pickaxe) and armor into a showcase, calls the item null. Also, the buying player might not realize the fact the item they are buying is almost worthless (worst case).

Suggested solutions:
1. Don't let sellers sell used items
2. Let them sell the items used, but warn the buyer
3. Add a config option that implements the above.
