Problem/Bug Cannot connect to server

I´ve got this error in Console when a player trying to join server after i delete one of my world where he was.
When a player wants to connect to the server he gets the message "Internal server error"

Code:

> 11:25:48 [SEVERE] Cannot Hotload Dim: Could not get provider type for dimension 15, does not exist
> 11:25:48 [INFO] Disconnecting iCrys [/80.188.67.139:52608]: Internal server error
>2016-09-24 11:25:48 [SEVERE] [ForgeModLoader] Error handling login related packet - connection from iCrys [/80.188.67.139:52608] refused
net.minecraft.util.ReportedException: Loading entity NBT
at net.minecraft.entity.Entity.func_70020_e(Entity.java:1830)
at net.minecraft.world.storage.SaveHandler.func_75752_b(SaveHandler.java:315)
at net.minecraft.server.management.ServerConfigurationManager.func_72380_a(ServerConfigurationManager.java:294)
at net.minecraft.server.management.ServerConfigurationManager.func_72355_a(ServerConfigurationManager.java:140)
at net.minecraft.network.NetLoginHandler.completeConnection(NetLoginHandler.java:215)
at cpw.mods.fml.common.network.FMLNetworkHandler.handleClientConnection(FMLNetworkHandler.java:171)
at cpw.mods.fml.common.network.FMLNetworkHandler.onConnectionReceivedFromClient(FMLNetworkHandler.java:124)
at net.minecraft.network.NetLoginHandler.func_72529_d(NetLoginHandler.java:191)
at net.minecraft.network.NetLoginHandler.func_72532_c(NetLoginHandler.java:79)
at net.minecraft.server.ServerListenThread.func_71766_a(ServerListenThread.java:57)
at net.minecraft.server.dedicated.DedicatedServerListenThread.func_71747_b(SourceFile:29)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:847)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:320)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:716)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:600)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)
Caused by: java.lang.NullPointerException
11:25:48 [WARNING] Failed to handle packet for iCrys [/80.188.67.139:52608]: net.minecraft.util.ReportedException: Loading entity NBT
net.minecraft.util.ReportedException: Loading entity NBT
at net.minecraft.entity.Entity.func_70020_e(Entity.java:1830)
at net.minecraft.world.storage.SaveHandler.func_75752_b(SaveHandler.java:315)
at net.minecraft.server.management.ServerConfigurationManager.func_72380_a(ServerConfigurationManager.java:294)
at net.minecraft.server.management.ServerConfigurationManager.func_72355_a(ServerConfigurationManager.java:140)
at net.minecraft.network.NetLoginHandler.completeConnection(NetLoginHandler.java:215)
at cpw.mods.fml.common.network.FMLNetworkHandler.handleClientConnection(FMLNetworkHandler.java:171)
at cpw.mods.fml.common.network.FMLNetworkHandler.onConnectionReceivedFromClient(FMLNetworkHandler.java:124)
at net.minecraft.network.NetLoginHandler.func_72529_d(NetLoginHandler.java:191)
at net.minecraft.network.NetLoginHandler.func_72532_c(NetLoginHandler.java:79)
at net.minecraft.server.ServerListenThread.func_71766_a(ServerListenThread.java:57)
at net.minecraft.server.dedicated.DedicatedServerListenThread.func_71747_b(SourceFile:29)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:847)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:320)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:716)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:600)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)
Caused by: java.lang.NullPointerException