Bukkit

What steps will reproduce the problem?
1. Joining the world the lobby is in
2. exiting the game and entering the lobby
3.

What is the expected output? What do you see instead?
one extra emerald per worldjoin

What version of the product are you using?
checked that this problem occurs both on the latest 1.7.2 and 1.7.9 build

Do you have an error log of what happened?
no error log, simply an extra emerald

Please provide any additional information below.
it is annoying :P