strange BA error?

2013-07-15 14:03:36 [INFO] Done (43.693s)! For help, type "help" or "?"
2013-07-15 14:03:36 [WARNING] [BattleArena] Task #65 for BattleArena v3.9.1.3 generated an exception
java.lang.NullPointerException
	at mc.alk.arena.serializers.SignSerializer.loadAll(SignSerializer.java:26)
	at mc.alk.arena.BattleArena$1.run(BattleArena.java:214)
	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)