MundoSk + ProtocolLib + Citizens error

[Goetheus]

Hi everybody!

I use MundoSk, and I recently installed ProtocolLib to use packets!
But, after installation, I get a big error when I try to connect to the server. And I can't go in :/

I discovered the source of the problem : an NPC! O_o
Without the spawned NPC, I can login. If I spawn it in game, I'm kick with the same error!

[17:17:41 ERROR]: [MundoSK] Unhandled exception occured in onPacketSending(PacketEvent) for MundoSK
java.lang.NullPointerException
        at com.pie.tlatoani.Tablist.TabListManager$1.onPacketSending(TabListManager.java:77) ~[MundoSK.jar:?]
        at com.comphenix.protocol.injector.SortedPacketListenerList.invokeSendingListener(SortedPacketListenerList.java:195) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.SortedPacketListenerList.invokePacketSending(SortedPacketListenerList.java:149) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.PacketFilterManager.handlePacket(PacketFilterManager.java:608) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.PacketFilterManager.invokePacketSending(PacketFilterManager.java:584) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.netty.ProtocolInjector.packetQueued(ProtocolInjector.java:309) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.netty.ProtocolInjector.onPacketSending(ProtocolInjector.java:269) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.netty.ChannelInjector.processSending(ChannelInjector.java:396) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.netty.ChannelInjector.access$500(ChannelInjector.java:77) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.netty.ChannelInjector$5.handleScheduled(ChannelInjector.java:362) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.netty.ChannelInjector$5.onMessageScheduled(ChannelInjector.java:330) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.netty.ChannelProxy$2.schedulingRunnable(ChannelProxy.java:127) [ProtocolLib.jar:4.2.1]
        at com.comphenix.protocol.injector.netty.EventLoopProxy.execute(EventLoopProxy.java:95) [ProtocolLib.jar:4.2.1]
        at net.minecraft.server.v1_11_R1.NetworkManager.a(NetworkManager.java:194) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.NetworkManager.sendPacket(NetworkManager.java:143) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.PlayerConnection.sendPacket(PlayerConnection.java:1100) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.EntityTrackerEntry.updatePlayer(EntityTrackerEntry.java:344) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.citizensnpcs.nms.v1_11_R1.util.PlayerlistTrackerEntry.updatePlayer(PlayerlistTrackerEntry.java:44) [citizens-2.0.21-SNAPSHOT.jar:?]
        at net.minecraft.server.v1_11_R1.EntityTracker.a(EntityTracker.java:261) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.PlayerChunk.sendChunk(PlayerChunk.java:148) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.PlayerChunk.a(PlayerChunk.java:66) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.PlayerChunkMap.addPlayer(PlayerChunkMap.java:287) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.PlayerList.a(PlayerList.java:284) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.PlayerList.onPlayerJoin(PlayerList.java:362) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.PlayerList.a(PlayerList.java:160) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.LoginListener.b(LoginListener.java:147) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.LoginListener.F_(LoginListener.java:57) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.NetworkManager.a(NetworkManager.java:233) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.ServerConnection.c(ServerConnection.java:140) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.MinecraftServer.D(MinecraftServer.java:842) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.DedicatedServer.D(DedicatedServer.java:399) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.MinecraftServer.C(MinecraftServer.java:678) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.MinecraftServer.run(MinecraftServer.java:576) [spigot.jar:git-Spigot-3fb9445-6e3cec8]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_77]
[17:17:41 ERROR]: Parameters:
  net.minecraft.server.v1_11_R1.PacketPlayOutNamedEntitySpawn@56228069[
    a=265
    b=28973fe1-600b-20c3-ac42-09befee24232
    c=41.152
    d=45.0
    e=-65.5738
    f=-65
    g=0
    h=net.minecraft.server.v1_11_R1.DataWatcher@30d5862a
    i=<null>
  ]

Thank you for help!

EDIT: Thank you to @Snow-Pyon ! The issue is the version of MundoSk (1.7.4). MundoSk dev build are required!