Bukkit Error Report

2013-08-04 20:20:06 [WARNING] [Skript] Task #17 for Skript v1.4.9 generated an exception
java.lang.NullPointerException
	at ch.njol.skript.events.EvtPeriodical.execute(EvtPeriodical.java:82)
	at ch.njol.skript.events.EvtPeriodical.access$0(EvtPeriodical.java:78)
	at ch.njol.skript.events.EvtPeriodical$1.run(EvtPeriodical.java:60)
	at org.bukkit.craftbukkit.v1_6_R2.scheduler.CraftTask.run(CraftTask.java:53)
	at org.bukkit.craftbukkit.v1_6_R2.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345)
	at net.minecraft.server.v1_6_R2.MinecraftServer.t(MinecraftServer.java:522)
	at net.minecraft.server.v1_6_R2.DedicatedServer.t(DedicatedServer.java:226)
	at net.minecraft.server.v1_6_R2.MinecraftServer.s(MinecraftServer.java:486)
	at net.minecraft.server.v1_6_R2.MinecraftServer.run(MinecraftServer.java:419)
	at net.minecraft.server.v1_6_R2.ThreadServerApplication.run(SourceFile:582)