Bukkit

When snake targets player, and they TP to another world or location, I get this error.

2012-12-13 17:21:02 [SEVERE] Exception in thread "Timer-141"
2012-12-13 17:21:02 [SEVERE] java.lang.IllegalArgumentException: Cannot measure distance between WHCommunity and WarriorCats
2012-12-13 17:21:02 [SEVERE]     at org.bukkit.Location.distanceSquared(Location.java:381)
2012-12-13 17:21:02 [SEVERE]     at org.bukkit.Location.distance(Location.java:364)
2012-12-13 17:21:02 [SEVERE]     at me.ci.Snake$1.run(Snake.java:148)
2012-12-13 17:21:02 [SEVERE]     at java.util.TimerThread.mainLoop(Unknown Source)
2012-12-13 17:21:02 [SEVERE]     at java.util.TimerThread.run(Unknown Source)

-Phea