fixed dupe glitch

this fixes a dupe glitch, described here:
http://epochmod.com/forum/index.php?/topic/28493-alpha-release-single-currency-30-storage-default-hive-no-global-banking/page-15#entry182128

also fixes possible dupe glitching by other players around.

EDIT: theres no conflict with TNT's fix. you should take both in my opinion.