Bukkit

What steps will reproduce the problem?
1. when i do /ignoreall chat ok is hide but in console i have problems
2.
3.

What is the expected output? What do you see instead?

What version of the product are you using?
IgnoreAll v0.1

Do you have an error log of what happened?

18:37:04 [SCHWERWIEGEND] Could not pass event PlayerChatEvent to IgnoreAll
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:304)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
        at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:776)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:754)
        at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:34)
        at net.minecraft.server.NetworkManager.b(NetworkManager.java:246)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:102)
        at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:82)
        at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:559)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:451)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:839)
        at java.util.HashMap$KeyIterator.next(HashMap.java:874)
        at tk.nekotech.ignoreall.IgnoreAll.onPlayerChat(IgnoreAll.java:35)
        at sun.reflect.GeneratedMethodAccessor235.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302)
        ... 12 more

Please provide any additional information below.