Bug report

: [KitPvP] Task #12 for KitPvP v1.3 generated an exception
java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextEntry(Unknown Source) ~[?:1.7.0_51]
    at java.util.HashMap$KeyIterator.next(Unknown Source) ~[?:1.7.0_51]
    at me.oliver276.kitpvp.PlayerIdle.run(PlayerIdle.java:31) ~[?:?]
    at org.bukkit.craftbukkit.v1_7_R1.scheduler.CraftTask.run(CraftTask.java:67) ~[spigot(1).jar:git-Spigot-1309]
    at org.bukkit.craftbukkit.v1_7_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345) [spigot(1).jar:git-Spigot-1309]
    at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:612) [spigot(1).jar:git-Spigot-1309]
    at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:273) [spigot(1).jar:git-Spigot-1309]
    at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:560) [spigot(1).jar:git-Spigot-1309]
    at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:467) [spigot(1).jar:git-Spigot-1309]
    at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [spigot(1).jar:git-Spigot-1309]