[Need Help]

My client keeps crashing when I join my server, I don't know what to do. 

 

This is the error it give me on my server.

[21:12:03] [Server thread/ERROR] [FML]: FMLIndexedMessageCodec exception caught
io.netty.handler.codec.EncoderException: java.lang.RuntimeException: Undefined discriminator for message type journeymap.common.network.DimensionPermissionPacket in channel jm_dim_permission
        at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:106) ~[MessageToMessageEncoder.class:?]
        at io.netty.handler.codec.MessageToMessageCodec.write(MessageToMessageCodec.java:116) ~[MessageToMessageCodec.class:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738) ~[AbstractChannelHandlerContext.class:?]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:801) ~[AbstractChannelHandlerContext.class:?]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:814) ~[AbstractChannelHandlerContext.class:?]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:794) ~[AbstractChannelHandlerContext.class:?]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:831) ~[AbstractChannelHandlerContext.class:?]
        at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1032) ~[DefaultChannelPipeline.class:?]
        at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:296) ~[AbstractChannel.class:?]
        at net.minecraftforge.fml.common.network.simpleimpl.SimpleNetworkWrapper.sendTo(SimpleNetworkWrapper.java:250) [SimpleNetworkWrapper.class:?]
        at journeymap.common.network.PacketHandler.sendDimensionPacketToPlayer(PacketHandler.java:57) [PacketHandler.class:1.12.2-5.5.3]
        at journeymap.server.events.ForgeEvents.on(ForgeEvents.java:73) [ForgeEvents.class:1.12.2-5.5.3]
        at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_753_ForgeEvents_on_EntityJoinWorldEvent.invoke(.dynamic) [?:?]
        at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90) [ASMEventHandler.class:?]
        at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182) [EventBus.class:?]
        at net.minecraft.world.World.func_72838_d(World.java:1206) [amu.class:?]
        at net.minecraft.world.WorldServer.func_72838_d(WorldServer.java:1058) [oo.class:?]
        at net.minecraft.server.management.PlayerList.func_72377_c(PlayerList.java:377) [pl.class:?]
        at net.minecraft.server.management.PlayerList.initializeConnectionToPlayer(PlayerList.java:166) [pl.class:?]
        at shadows.fastbench.net.HijackedDedicatedPlayerList.initializeConnectionToPlayer(HijackedDedicatedPlayerList.java:19) [HijackedDedicatedPlayerList.class:?]
        at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.completeServerSideConnection(NetworkDispatcher.java:255) [NetworkDispatcher.class:?]
        at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.access$100(NetworkDispatcher.java:72) [NetworkDispatcher.class:?]
        at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher$1.func_73660_a(NetworkDispatcher.java:205) [NetworkDispatcher$1.class:?]
        at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:285) [gw.class:?]
        at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:180) [oz.class:?]
        at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:790) [MinecraftServer.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397) [nz.class:?]
        at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) [MinecraftServer.class:?]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_201]
Caused by: java.lang.RuntimeException: Undefined discriminator for message type journeymap.common.network.DimensionPermissionPacket in channel jm_dim_permission
        at net.minecraftforge.fml.common.network.FMLIndexedMessageToMessageCodec.encode(FMLIndexedMessageToMessageCodec.java:76) ~[FMLIndexedMessageToMessageCodec.class:?]
        at io.netty.handler.codec.MessageToMessageCodec$1.encode(MessageToMessageCodec.java:67) ~[MessageToMessageCodec$1.class:?]
        at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:88) ~[MessageToMessageEncoder.class:?]
        ... 29 more