Minecraft 1.5 Server Ticking entity / java.lang.NullPointerException

2013-03-21 15:29:06 [SEVERE] net.minecraft.server.v1_5_R1.ReportedException: Ticking entity
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.MinecraftServer.r(MinecraftServer.java:566)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.DedicatedServer.r(DedicatedServer.java:225)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.MinecraftServer.q(MinecraftServer.java:476)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.MinecraftServer.run(MinecraftServer.java:409)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.ThreadServerApplication.run(SourceFile:573)
2013-03-21 15:29:06 [SEVERE] Caused by: java.lang.NullPointerException
2013-03-21 15:29:06 [SEVERE] at java.util.LinkedList$ListItr.next(LinkedList.java:891)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.EntityPlayer.l_(EntityPlayer.java:171)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.World.entityJoinedWorld(World.java:1356)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.WorldServer.entityJoinedWorld(WorldServer.java:594)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.World.playerJoinedWorld(World.java:1337)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.World.tickEntities(World.java:1225)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.WorldServer.tickEntities(WorldServer.java:462)
2013-03-21 15:29:06 [SEVERE] at net.minecraft.server.v1_5_R1.MinecraftServer.r(MinecraftServer.java:562)
2013-03-21 15:29:06 [SEVERE] ... 4 more
2013-03-21 15:29:06 [SEVERE] Encountered an unexpected exception ReportedException
net.minecraft.server.v1_5_R1.ReportedException: Ticking entity
at net.minecraft.server.v1_5_R1.MinecraftServer.r(MinecraftServer.java:566)
at net.minecraft.server.v1_5_R1.DedicatedServer.r(DedicatedServer.java:225)
at net.minecraft.server.v1_5_R1.MinecraftServer.q(MinecraftServer.java:476)
at net.minecraft.server.v1_5_R1.MinecraftServer.run(MinecraftServer.java:409)
at net.minecraft.server.v1_5_R1.ThreadServerApplication.run(SourceFile:573)
Caused by: java.lang.NullPointerException
at java.util.LinkedList$ListItr.next(LinkedList.java:891)
at net.minecraft.server.v1_5_R1.EntityPlayer.l_(EntityPlayer.java:171)
at net.minecraft.server.v1_5_R1.World.entityJoinedWorld(World.java:1356)
at net.minecraft.server.v1_5_R1.WorldServer.entityJoinedWorld(WorldServer.java:594)
at net.minecraft.server.v1_5_R1.World.playerJoinedWorld(World.java:1337)
at net.minecraft.server.v1_5_R1.World.tickEntities(World.java:1225)
at net.minecraft.server.v1_5_R1.WorldServer.tickEntities(WorldServer.java:462)
at net.minecraft.server.v1_5_R1.MinecraftServer.r(MinecraftServer.java:562)
... 4 more