Bukkit

Currently Using Spigot 1.8.3
With Citizens2 build 1228  http://ci.citizensnpcs.co/job/Citizens2/1228/

I seem to be getting this error spammed on error logs as a result.

[20:45:26] [Server thread/ERROR]: Could not pass event EntityDeathEvent to CombatTag v6.3.2-SNAPSHOT
org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:305) ~[spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.craftbukkit.v1_8_R1.event.CraftEventFactory.callEntityDeathEvent(CraftEventFactory.java:363) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.EntityLiving.die(EntityLiving.java:868) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.EntityLiving.damageEntity(EntityLiving.java:806) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.EntityLiving.K(EntityLiving.java:173) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.EntityInsentient.K(EntityInsentient.java:149) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.Entity.s_(Entity.java:245) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.EntityLiving.s_(EntityLiving.java:1438) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.EntityInsentient.s_(EntityInsentient.java:193) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.World.entityJoinedWorld(World.java:1604) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.World.g(World.java:1579) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.World.tickEntities(World.java:1422) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.WorldServer.tickEntities(WorldServer.java:576) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:772) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:316) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:634) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java:537) [spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at java.lang.Thread.run(Thread.java:724) [?:1.7.0_25]
Caused by: java.lang.NoClassDefFoundError: net/minecraft/server/v1_8_R2/World
    at net.citizensnpcs.npc.CitizensNPCRegistry.getNPC(CitizensNPCRegistry.java:122) ~[?:?]
    at net.citizensnpcs.npc.CitizensNPCRegistry.isNPC(CitizensNPCRegistry.java:128) ~[?:?]
    at com.trc202.CombatTag.libs.npclib.citizens.CitizensNPCRegistry.isNPC(CitizensNPCRegistry.java:76) ~[?:?]
    at com.trc202.CombatTag.NPCManager.isNPC(NPCManager.java:55) ~[?:?]
    at com.trc202.CombatTagListeners.NoPvpEntityListener.onEntityDeath(NoPvpEntityListener.java:61) ~[?:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_25]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_25]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301) ~[spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    ... 20 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_8_R2.World
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:91) ~[spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.7.0_25]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.7.0_25]
    at net.citizensnpcs.npc.CitizensNPCRegistry.getNPC(CitizensNPCRegistry.java:122) ~[?:?]
    at net.citizensnpcs.npc.CitizensNPCRegistry.isNPC(CitizensNPCRegistry.java:128) ~[?:?]
    at com.trc202.CombatTag.libs.npclib.citizens.CitizensNPCRegistry.isNPC(CitizensNPCRegistry.java:76) ~[?:?]
    at com.trc202.CombatTag.NPCManager.isNPC(NPCManager.java:55) ~[?:?]
    at com.trc202.CombatTagListeners.NoPvpEntityListener.onEntityDeath(NoPvpEntityListener.java:61) ~[?:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_25]
    at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_25]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301) ~[spigot_server.jar:git-Spigot-c3c767f-33d5de3]
    ... 20 more