java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
at java.util.HashMap$ValueIterator.next(Unknown Source)
at net.minecraft.chunk.Chunk.onChunkUnload(Chunk.java:669)
at net.minecraft.chunk.ChunkProviderClient.func_539_c(ChunkProviderClient.java:51)
at net.minecraft.world.WorldClient.doPreChunk(WorldClient.java:128)
at net.minecraft.network.NetClientHandler.handlePreChunk(NetClientHandler.java:485)
at net.minecraft.packet.Packet50PreChunk.processPacket(Packet50PreChunk.java:39)
at net.minecraft.network.NetworkManager.processReadPackets(NetworkManager.java:204)
at net.minecraft.network.NetClientHandler.processReadPackets(NetClientHandler.java:167)
at net.minecraft.world.WorldClient.tick(WorldClient.java:70)
at net.minecraft.client.Minecraft.runTick(Minecraft.java:1248)
at net.minecraft.client.Minecraft.run(Minecraft.java:541)
at java.lang.Thread.run(Unknown Source)