whats error

[23:00:54] [Craft Scheduler Thread - 5/ERROR]: [MythicMobs] [SCHEDULER] Exception thrown whilst executing task
[23:00:54] [Craft Scheduler Thread - 5/WARN]: java.lang.NullPointerException
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at io.lumine.xikage.mythicmobs.mobs.MobManager.getActiveMobs(MobManager.java:239)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at io.lumine.xikage.mythicmobs.skills.SkillManager.runTimerSkills(SkillManager.java:298)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at io.lumine.xikage.mythicmobs.clock.MythicMobsAsyncClock.run(MythicMobsAsyncClock.java:21)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at io.lumine.xikage.mythicmobs.utils.Delegates$RunnableToConsumer.accept(Delegates.java:63)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at io.lumine.xikage.mythicmobs.utils.Schedulers$LumineTask.run(Schedulers.java:164)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at org.bukkit.craftbukkit.v1_15_R1.scheduler.CraftTask.run(CraftTask.java:81)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at org.bukkit.craftbukkit.v1_15_R1.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:54)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[23:00:54] [Craft Scheduler Thread - 5/WARN]: 	at java.lang.Thread.run(Thread.java:748)
[23:00:54] [Server thread/ERROR]: Could not pass event EntityDamageEvent to MythicMobs v4.9.0-SNAPSHOT-3186
org.bukkit.event.EventException: null
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:320) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:529) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:514) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at org.bukkit.craftbukkit.v1_15_R1.event.CraftEventFactory.callEvent(CraftEventFactory.java:230) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at org.bukkit.craftbukkit.v1_15_R1.event.CraftEventFactory.callEntityDamageEvent(CraftEventFactory.java:923) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at org.bukkit.craftbukkit.v1_15_R1.event.CraftEventFactory.handleEntityDamageEvent(CraftEventFactory.java:905) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at org.bukkit.craftbukkit.v1_15_R1.event.CraftEventFactory.handleEntityDamageEvent(CraftEventFactory.java:766) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at org.bukkit.craftbukkit.v1_15_R1.event.CraftEventFactory.handleLivingEntityDamageEvent(CraftEventFactory.java:955) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.EntityLiving.damageEntity0(EntityLiving.java:1624) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.EntityHuman.damageEntity0(EntityHuman.java:862) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.EntityLiving.damageEntity(EntityLiving.java:1028) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.EntityHuman.damageEntity(EntityHuman.java:785) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.EntityPlayer.damageEntity(EntityPlayer.java:659) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.citizensnpcs.nms.v1_15_R1.entity.EntityHumanNPC.damageEntity(EntityHumanNPC.java:143) ~[?:?]
	at net.minecraft.server.v1_15_R1.EntityLiving.entityBaseTick(EntityLiving.java:246) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.citizensnpcs.nms.v1_15_R1.entity.EntityHumanNPC.livingEntityBaseTick(EntityHumanNPC.java:321) ~[?:?]
	at net.citizensnpcs.nms.v1_15_R1.entity.EntityHumanNPC.tick(EntityHumanNPC.java:415) ~[?:?]
	at net.minecraft.server.v1_15_R1.WorldServer.entityJoinedWorld(WorldServer.java:626) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.World.a(World.java:718) [bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.WorldServer.doTick(WorldServer.java:395) [bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.MinecraftServer.b(MinecraftServer.java:1082) [bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.DedicatedServer.b(DedicatedServer.java:399) [bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.MinecraftServer.a(MinecraftServer.java:984) [bukkit.jar:git-Spigot-800b93f-e911c70]
	at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:824) [bukkit.jar:git-Spigot-800b93f-e911c70]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_232]
Caused by: java.lang.NullPointerException
	at io.lumine.xikage.mythicmobs.mobs.MobManager.isActiveMob(MobManager.java:266) ~[?:?]
	at io.lumine.xikage.mythicmobs.adapters.bukkit.listeners.MobListeners.damagePassthroughEvent(MobListeners.java:68) ~[?:?]
	at sun.reflect.GeneratedMethodAccessor166.invoke(Unknown Source) ~[?:?]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_232]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_232]
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:316) ~[bukkit.jar:git-Spigot-800b93f-e911c70]
	... 25 more