Error

13:15:34 [SCHWERWIEGEND] Could not pass event PlayerJoinEvent to McMmoAp
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:303)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:459)
        at net.minecraft.server.ServerConfigurationManager.c(ServerConfigurationManager.jav
        at net.minecraft.server.NetLoginHandler.b(NetLoginHandler.java:129)
        at net.minecraft.server.NetLoginHandler.a(NetLoginHandler.java:94)
        at net.minecraft.server.Packet1Login.handle(SourceFile:68)
        at net.minecraft.server.NetworkManager.b(NetworkManager.java:229)
        at net.minecraft.server.NetLoginHandler.a(NetLoginHandler.java:48)
        at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:61)
        at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:551)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:449)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: java.lang.NullPointerException
        at me.tagette.mcmmoap.APPowerLevel.getNextRankGroup(APPowerLevel.java:106)
        at me.tagette.mcmmoap.APPowerLevel.tryPromote(APPowerLevel.java:62)
        at me.tagette.mcmmoap.APPlayerListener.onPlayerJoin(APPlayerListener.java:28)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301)
        ... 12 more