Reproduction steps:

Using a single player world in the most recent forge build.

Put the following files in a folder in the "worlds" folder of the "Terrain Control" folder of your "mods" folder:

https://www.mediafire.com/?p5gyr6nid24zl2r

Create a new world, using Terrain Control as the generator. Name it the same name as the folder you put into the "worlds" folder.

Set the seed to 1. (Might work with other seeds, but I'm going for a ironclad repro.)

Start the new map.

It crashes to the desktop.

Stacktrace:

[13:25:51] [Server thread/ERROR] [FML]: HandshakeCompletionHandler exception
java.lang.NullPointerException
at com.khorn.terraincontrol.configuration.WorldSettings.writeToStream(WorldSettings.java:460) ~[WorldSettings.class:?]
at com.khorn.terraincontrol.forge.events.PlayerTracker.onPlayerLogin(PlayerTracker.java:50) ~[PlayerTracker.class:?]
at cpw.mods.fml.common.eventhandler.ASMEventHandler_82_PlayerTracker_onPlayerLogin_PlayerLoggedInEvent.invoke(.dynamic) ~[?:?]
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:51) ~[ASMEventHandler.class:?]
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:122) ~[EventBus.class:?]
at cpw.mods.fml.common.FMLCommonHandler.firePlayerLoggedIn(FMLCommonHandler.java:549) ~[FMLCommonHandler.class:?]
at net.minecraft.server.management.ServerConfigurationManager.initializeConnectionToPlayer(ServerConfigurationManager.java:193) ~[ServerConfigurationManager.class:?]
at cpw.mods.fml.common.network.handshake.NetworkDispatcher.completeServerSideConnection(NetworkDispatcher.java:173) ~[NetworkDispatcher.class:?]
at cpw.mods.fml.common.network.handshake.NetworkDispatcher.completeHandshake(NetworkDispatcher.java:446) ~[NetworkDispatcher.class:?]
at cpw.mods.fml.common.network.internal.HandshakeCompletionHandler.channelRead0(HandshakeCompletionHandler.java:17) ~[HandshakeCompletionHandler.class:?]
at cpw.mods.fml.common.network.internal.HandshakeCompletionHandler.channelRead0(HandshakeCompletionHandler.java:11) ~[HandshakeCompletionHandler.class:?]
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:98) ~[SimpleChannelInboundHandler.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103) [MessageToMessageDecoder.class:?]
at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) [MessageToMessageCodec.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) [DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:785) [DefaultChannelPipeline.class:?]
at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) [EmbeddedChannel.class:?]
at cpw.mods.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:86) [FMLProxyPacket.class:?]
at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:247) [NetworkManager.class:?]
at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:182) [NetworkSystem.class:?]
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:736) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:624) [MinecraftServer.class:?]
at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:118) [IntegratedServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:495) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:762) [MinecraftServer$2.class:?]
[13:25:51] [Server thread/ERROR] [FML]: There was a critical exception handling a packet on channel FML
java.lang.NullPointerException
at com.khorn.terraincontrol.configuration.WorldSettings.writeToStream(WorldSettings.java:460) ~[WorldSettings.class:?]
at com.khorn.terraincontrol.forge.events.PlayerTracker.onPlayerLogin(PlayerTracker.java:50) ~[PlayerTracker.class:?]
at cpw.mods.fml.common.eventhandler.ASMEventHandler_82_PlayerTracker_onPlayerLogin_PlayerLoggedInEvent.invoke(.dynamic) ~[?:?]
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:51) ~[ASMEventHandler.class:?]
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:122) ~[EventBus.class:?]
at cpw.mods.fml.common.FMLCommonHandler.firePlayerLoggedIn(FMLCommonHandler.java:549) ~[FMLCommonHandler.class:?]
at net.minecraft.server.management.ServerConfigurationManager.initializeConnectionToPlayer(ServerConfigurationManager.java:193) ~[ServerConfigurationManager.class:?]
at cpw.mods.fml.common.network.handshake.NetworkDispatcher.completeServerSideConnection(NetworkDispatcher.java:173) ~[NetworkDispatcher.class:?]
at cpw.mods.fml.common.network.handshake.NetworkDispatcher.completeHandshake(NetworkDispatcher.java:446) ~[NetworkDispatcher.class:?]
at cpw.mods.fml.common.network.internal.HandshakeCompletionHandler.channelRead0(HandshakeCompletionHandler.java:17) ~[HandshakeCompletionHandler.class:?]
at cpw.mods.fml.common.network.internal.HandshakeCompletionHandler.channelRead0(HandshakeCompletionHandler.java:11) ~[HandshakeCompletionHandler.class:?]
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:98) ~[SimpleChannelInboundHandler.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) ~[DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) ~[DefaultChannelHandlerContext.class:?]
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103) ~[MessageToMessageDecoder.class:?]
at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.class:?]
at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:337) ~[DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:323) ~[DefaultChannelHandlerContext.class:?]
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:785) ~[DefaultChannelPipeline.class:?]
at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) ~[EmbeddedChannel.class:?]
at cpw.mods.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:86) [FMLProxyPacket.class:?]
at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:247) [NetworkManager.class:?]
at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:182) [NetworkSystem.class:?]
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:736) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:624) [MinecraftServer.class:?]
at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:118) [IntegratedServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:495) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:762) [MinecraftServer$2.class:?]
[13:25:51] [Server thread/ERROR]: Encountered an unexpected exception
net.minecraft.util.ReportedException: Ticking memory connection
at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:198) ~[NetworkSystem.class:?]
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:736) ~[MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:624) ~[MinecraftServer.class:?]
at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:118) ~[IntegratedServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:495) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:762) [MinecraftServer$2.class:?]
Caused by: java.lang.NullPointerException
at cpw.mods.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:110) ~[FMLProxyPacket.class:?]
at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:247) ~[NetworkManager.class:?]
at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:182) ~[NetworkSystem.class:?]
... 5 more

That stack trace is really ugly. Is there a better way of posting them on github? Or should I be putting them on pastebin or something instead?

Found it! Your custom biomes setting contains the following:

Desert:78, DesertHills:79, Beach:80, TAOceanRich:81, River:82,

You cannot give vanilla biomes a different id. This causes a crash later on. Fixed it by removing vanilla biomes from CustomBiomes.

You are excellent, sir. Sorry I accused your code of being faulty when it was really user error.

There was actually a bug: TC should never crash, it should print an error message when the config is invalid. The code was faulty, just not in the place you expected it to be. 😄

TC is a very complex plugin where every feature can interact with every feature in interesting ways. @talonos2, you are doing excellent work with all this bug hunting. Thanks to you many bugs have been fixed.