This error is arising on creaturespawnevent.

01.07 09:56:42 [Multicraft] Skipped 3 lines due to rate limit (30/s)
01.07 09:56:27 [Server] INFO at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_75]
01.07 09:56:27 [Server] INFO at sun.reflect.GeneratedMethodAccessor34.invoke(Unknown Source) ~[?:?]
01.07 09:56:27 [Server] INFO at us.deathmarine.diablodrops.listeners.MobListener.onSpawn(MobListener.java:53) ~[?:?]
01.07 09:56:27 [Server] INFO at us.deathmarine.diablodrops.drops.DropsAPI.getItem(DropsAPI.java:358) ~[?:?]
01.07 09:56:27 [Server] INFO at us.deathmarine.diablodrops.drops.DropsAPI.getItem(DropsAPI.java:546) ~[?:?]
01.07 09:56:27 [Server] INFO at us.deathmarine.diablodrops.drops.DropsAPI.colorPicker(DropsAPI.java:68) ~[?:?]
01.07 09:56:27 [Server] INFO at java.util.Random.nextInt(Random.java:300) ~[?:1.7.0_75]
01.07 09:56:27 [Server] INFO Caused by: java.lang.IllegalArgumentException: n must be positive
01.07 09:56:27 [Server] INFO at java.lang.Thread.run(Thread.java:745) [?:1.7.0_75]
01.07 09:56:27 [Server] INFO at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java:537) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:634) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:316) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:756) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at net.minecraft.server.v1_8_R1.WorldServer.doTick(WorldServer.java:214) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at net.minecraft.server.v1_8_R1.SpawnerCreature.a(SpawnerCreature.java:182) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at net.minecraft.server.v1_8_R1.World.addEntity(World.java:1014) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at org.bukkit.craftbukkit.v1_8_R1.event.CraftEventFactory.callCreatureSpawnEvent(CraftEventFactory.java:275) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:305) ~[spigot.jar:git-Spigot-c3c767f-33d5de3]
01.07 09:56:27 [Server] INFO org.bukkit.event.EventException
01.07 09:56:27 [Server] ERROR Could not pass event CreatureSpawnEvent to DiabloDrops v2.6