[10:47:13 WARN]: [ThePlague] Task #167 for ThePlague v1.0 generated an exception

java.lang.IllegalStateException: Not scheduled yet
        at org.bukkit.scheduler.BukkitRunnable.getTaskId(BukkitRunnable.java:134
) ~[Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efeddf-b3074jnks]
        at org.bukkit.scheduler.BukkitRunnable.cancel(BukkitRunnable.java:18) ~[
Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efeddf-b3074jnks]
        at me.mrkirby153.plugins.ThePlague.arena.Arena.run(Arena.java:158) ~[?:?
]
        at org.bukkit.craftbukkit.v1_7_R3.scheduler.CraftTask.run(CraftTask.java
:53) ~[Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efeddf-b3074jnks]
        at org.bukkit.craftbukkit.v1_7_R3.scheduler.CraftScheduler.mainThreadHea
rtbeat(CraftScheduler.java:345) [Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efe
ddf-b3074jnks]
        at net.minecraft.server.v1_7_R3.MinecraftServer.v(MinecraftServer.java:6
00) [Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efeddf-b3074jnks]
        at net.minecraft.server.v1_7_R3.DedicatedServer.v(DedicatedServer.java:2
60) [Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efeddf-b3074jnks]
        at net.minecraft.server.v1_7_R3.MinecraftServer.u(MinecraftServer.java:5
58) [Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efeddf-b3074jnks]
        at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java
:469) [Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efeddf-b3074jnks]
        at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:6
28) [Bukkit-1.7.9.jar:git-Bukkit-1.7.2-R0.3-59-g6efeddf-b3074jnks]