Bug with missile skill

java.util.ConcurrentModificationException
    at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
    at java.util.ArrayList$Itr.next(ArrayList.java:851)
    at org.bukkit.craftbukkit.v1_8_R3.CraftWorld.getLivingEntities(CraftWorld.java:667)
    at io.lumine.xikage.MythicLib.Adapters.Bukkit.BukkitWorld.getLivingEntities(BukkitWorld.java:52)
    at...