Error:
16:36:31 [WARNING] Failed to handle packet: java.util.ConcurrentModificationException
java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
        at java.util.HashMap$KeyIterator.next(HashMap.java:828)
        at net.minecraft.server.EntityLiving.aK(EntityLiving.java:1409)
        at net.minecraft.server.EntityLiving.aA(EntityLiving.java:355)
        at net.minecraft.server.Entity.F_(Entity.java:268)
        at net.minecraft.server.EntityLiving.F_(EntityLiving.java:435)
        at net.minecraft.server.EntityHuman.F_(EntityHuman.java:159)
        at net.minecraft.server.EntityPlayer.a(EntityPlayer.java:228)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:341)
        at net.minecraft.server.Packet10Flying.handle(SourceFile:126)
        at net.minecraft.server.NetworkManager.b(NetworkManager.java:229)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:113)
        at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78)
        at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:567)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:459)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Spells:
    damage:
        spell-class: ".targeted.PotionEffectSpell"
        type: 15
        duration: 8
        targeted: false
        effects:
            - caster itemspray 331 8 20 0.25
            - caster itemspray 352 4 30 0.2
    damage_trigger:
        spell-class: ".PassiveSpell"
        cast-without-target: true
        triggers:
            - takedamage
        spells:
            - damage