MobDungeon bug

[WARNING] Task of 'MobDungeon' generated an exception
java.lang.NullPointerException
	at de.kumpelblase2.mobdungeon.BaseClasses.MDLevel.SpawnMobs(MDLevel.java:404)
	at de.kumpelblase2.mobdungeon.BaseClasses.MDLevel.SpawnMobs(MDLevel.java:323)
	at de.kumpelblase2.mobdungeon.BaseClasses.MDLevel.startWave(MDLevel.java:449)
	at de.kumpelblase2.mobdungeon.BaseClasses.DelayedWaveStart.run(DelayedWaveStart.java:41)
	at com.bergerkiller.bukkit.nolagg.examine.TimedWrapper.run(TimedWrapper.java:20)
	at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:126)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:520)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:452)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:490)