Stack Trace, Creeper spawn

java.lang.Exception: Stack trace
        at java.lang.Thread.dumpStack(Unknown Source)
        at MobSpawnDetector$Detector.onMobSpawn(MobSpawnDetector.java:27)
        at PluginLoader.callHook(PluginLoader.java:590)
        at OWorldServer.b(OWorldServer.java:128)
        at OTileEntityMobSpawner.g_(OTileEntityMobSpawner.java:69)
        at OWorld.e(OWorld.java:914)
        at net.minecraft.server.MinecraftServer.h(SourceFile:350)
        at net.minecraft.server.MinecraftServer.run(SourceFile:286)
        at OThreadServerApplication.run(SourceFile:394)
java.lang.Exception: Stack trace
        at java.lang.Thread.dumpStack(Unknown Source)
        at MobSpawnDetector$Detector.onMobSpawn(MobSpawnDetector.java:27)
        at PluginLoader.callHook(PluginLoader.java:590)
        at OWorld.b(OWorld.java:672)
        at OWorldServer.b(OWorldServer.java:131)
        at OTileEntityMobSpawner.g_(OTileEntityMobSpawner.java:69)
        at OWorld.e(OWorld.java:914)
        at net.minecraft.server.MinecraftServer.h(SourceFile:350)
        at net.minecraft.server.MinecraftServer.run(SourceFile:286)
        at OThreadServerApplication.run(SourceFile:394)