Removed an errant nextId decrement that would occur even if the class was already registered and already had an ID. This makes the teetering tower of glass shards slightly less fragile... slightly. git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@7722 75d07b2b-3a1a-0410-a2c5-0572b91ccdca