Bukkit

Error below appears randomly in console. Using version 3.17 and Spigot 1.7.9
Let me know if I can provide further help.

[05:17:36] [Server thread/ERROR]: Could not pass event EntityDamageByEntityEvent to MobCatcher v3.17
org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:299) ~[spigot.jar:git-Spigot-1543]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-1543]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot.jar:git-Spigot-1543]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot.jar:git-Spigot-1543]
    at org.bukkit.craftbukkit.v1_7_R3.event.CraftEventFactory.callEvent(CraftEventFactory.java:109) [spigot.jar:git-Spigot-1543]
    at org.bukkit.craftbukkit.v1_7_R3.event.CraftEventFactory.callEntityDamageEvent(CraftEventFactory.java:550) [spigot.jar:git-Spigot-1543]
    at org.bukkit.craftbukkit.v1_7_R3.event.CraftEventFactory.handleEntityDamageEvent(CraftEventFactory.java:463) [spigot.jar:git-Spigot-1543]
    at org.bukkit.craftbukkit.v1_7_R3.event.CraftEventFactory.handleLivingEntityDamageEvent(CraftEventFactory.java:572) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.EntityLiving.d(EntityLiving.java:1009) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.EntityLiving.damageEntity(EntityLiving.java:683) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.EntityAnimal.damageEntity(SourceFile:145) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.EntityEgg.a(EntityEgg.java:26) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.EntityProjectile.h(EntityProjectile.java:155) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.World.entityJoinedWorld(World.java:1602) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.World.playerJoinedWorld(World.java:1577) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.World.tickEntities(World.java:1442) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.WorldServer.tickEntities(WorldServer.java:516) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.MinecraftServer.v(MinecraftServer.java:703) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.DedicatedServer.v(DedicatedServer.java:284) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.MinecraftServer.u(MinecraftServer.java:584) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java:490) [spigot.jar:git-Spigot-1543]
    at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:628) [spigot.jar:git-Spigot-1543]
Caused by: java.lang.NullPointerException
    at me.jordan.mobcatcher.MobCatcher.vaultCost(MobCatcher.java:1134) ~[?:?]
    at me.jordan.mobcatcher.MCCaptureEvent.dropCapture(MCCaptureEvent.java:667) ~[?:?]
    at me.jordan.mobcatcher.MCCaptureEvent.Capture(MCCaptureEvent.java:570) ~[?:?]
    at me.jordan.mobcatcher.MCCaptureEvent.OnEntityDamage(MCCaptureEvent.java:176) ~[?:?]
    at sun.reflect.GeneratedMethodAccessor292.invoke(Unknown Source) ~[?:?]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.7.0_67]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.7.0_67]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:296) ~[spigot.jar:git-Spigot-1543]
    ... 21 more

Im not able to replicate the error on a non-Spigot server. Unfortunately, these spigot bugs are very difficult to fix as Spigot makes changes on Craftbukkit that potentially breaks things.

Sorry.