Could not pass event EntityDeathEvent to MCTest v1.0
org.bukkit.event.EventException: null
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:320) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:529) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:514) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at org.bukkit.craftbukkit.v1_14_R1.event.CraftEventFactory.callEntityDeathEvent(CraftEventFactory.java:708) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityLiving.d(EntityLiving.java:1365) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityLiving.die(EntityLiving.java:1322) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityLiving.damageEntity(EntityLiving.java:1169) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityBat.damageEntity(EntityBat.java:185) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.Entity.burnFromLava(Entity.java:441) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.Entity.entityBaseTick(Entity.java:395) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityLiving.entityBaseTick(EntityLiving.java:236) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityInsentient.entityBaseTick(EntityInsentient.java:210) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.Entity.tick(Entity.java:346) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityLiving.tick(EntityLiving.java:2217) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityInsentient.tick(EntityInsentient.java:273) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.EntityBat.tick(EntityBat.java:86) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.WorldServer.entityJoinedWorld(WorldServer.java:568) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.World.a(World.java:745) [spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.WorldServer.doTick(WorldServer.java:344) [spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.MinecraftServer.b(MinecraftServer.java:1069) [spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.DedicatedServer.b(DedicatedServer.java:396) [spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.MinecraftServer.a(MinecraftServer.java:971) [spigot.jar:git-Spigot-9de398a-9c887d4]
        at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:816) [spigot.jar:git-Spigot-9de398a-9c887d4]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_201]
Caused by: java.lang.NullPointerException
        at de.deda.mctest.program.ChallengeSystem.OnPlayerKillMob(ChallengeSystem.java:279) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_201]
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_201]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_201]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_201]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:316) ~[spigot.jar:git-Spigot-9de398a-9c887d4]
        ... 24 more