error

2013-03-06 19:13:38 [WARNING] Failed to handle packet for MrBrasta/25.151.120.0: java.lang.NullPointerException
java.lang.NullPointerException
	at net.minecraft.server.v1_4_R1.PlayerList.changeDimension(PlayerList.java:463)
	at net.minecraft.server.v1_4_R1.EntityPlayer.b(EntityPlayer.java:344)
	at net.minecraft.server.v1_4_R1.BlockEnderPortal.a(BlockEnderPortal.java:47)
	at net.minecraft.server.v1_4_R1.Entity.D(Entity.java:748)
	at net.minecraft.server.v1_4_R1.Entity.move(Entity.java:700)
	at net.minecraft.server.v1_4_R1.EntityLiving.e(EntityLiving.java:1065)
	at net.minecraft.server.v1_4_R1.EntityHuman.e(EntityHuman.java:1141)
	at net.minecraft.server.v1_4_R1.EntityLiving.c(EntityLiving.java:1306)
	at net.minecraft.server.v1_4_R1.EntityHuman.c(EntityHuman.java:306)
	at net.minecraft.server.v1_4_R1.EntityLiving.j_(EntityLiving.java:534)
	at net.minecraft.server.v1_4_R1.EntityHuman.j_(EntityHuman.java:155)
	at net.minecraft.server.v1_4_R1.EntityPlayer.g(EntityPlayer.java:194)
	at net.minecraft.server.v1_4_R1.PlayerConnection.a(PlayerConnection.java:352)
	at net.minecraft.server.v1_4_R1.Packet10Flying.handle(SourceFile:136)
	at net.minecraft.server.v1_4_R1.NetworkManager.b(NetworkManager.java:290)
	at net.minecraft.server.v1_4_R1.PlayerConnection.d(PlayerConnection.java:113)
	at net.minecraft.server.v1_4_R1.ServerConnection.b(SourceFile:39)
	at net.minecraft.server.v1_4_R1.DedicatedServerConnection.b(SourceFile:30)
	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:598)
	at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
	at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:494)
	at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:427)
	at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)