Network Exception

console

io.netty.handler.codec.DecoderException: java.lang.NullPointerException: Undefined message for discriminator 0 in channel smithscore-structures
	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:99) ~[MessageToMessageDecoder.class:4.0.23.Final]
	at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111) ~[MessageToMessageCodec.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787) [DefaultChannelPipeline.class:4.0.23.Final]
	at io.netty.channel.embedded.EmbeddedChannel.writeInbound(EmbeddedChannel.java:169) [EmbeddedChannel.class:4.0.23.Final]
	at net.minecraftforge.fml.common.network.internal.FMLProxyPacket.processPacket(FMLProxyPacket.java:90) [FMLProxyPacket.class:?]
	at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:158) [NetworkManager.class:?]
	at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:54) [NetworkManager.class:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [SimpleChannelInboundHandler.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.handleClientSideCustomPacket(NetworkDispatcher.java:390) [NetworkDispatcher.class:?]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:256) [NetworkDispatcher.class:?]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:54) [NetworkDispatcher.class:?]
	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [SimpleChannelInboundHandler.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [AbstractChannelHandlerContext.class:4.0.23.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787) [DefaultChannelPipeline.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel.finishPeerRead(LocalChannel.java:326) [LocalChannel.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel.access$400(LocalChannel.java:45) [LocalChannel.class:4.0.23.Final]
	at io.netty.channel.local.LocalChannel$5.run(LocalChannel.java:312) [LocalChannel$5.class:4.0.23.Final]
	at io.netty.channel.local.LocalEventLoop.run(LocalEventLoop.java:33) [LocalEventLoop.class:4.0.23.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) [SingleThreadEventExecutor$2.class:4.0.23.Final]
	at java.lang.Thread.run(Thread.java:745) [?:1.7.0_79]
Caused by: java.lang.NullPointerException: Undefined message for discriminator 0 in channel smithscore-structures
	at net.minecraftforge.fml.common.network.FMLIndexedMessageToMessageCodec.decode(FMLIndexedMessageToMessageCodec.java:77) ~[FMLIndexedMessageToMessageCodec.class:?]
	at net.minecraftforge.fml.common.network.FMLIndexedMessageToMessageCodec.decode(FMLIndexedMessageToMessageCodec.java:21) ~[FMLIndexedMessageToMessageCodec.class:?]
	at io.netty.handler.codec.MessageToMessageCodec$2.decode(MessageToMessageCodec.java:81) ~[MessageToMessageCodec$2.class:4.0.23.Final]
	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:89) ~[MessageToMessageDecoder.class:4.0.23.Final]
	... 24 more