error log

[SEVERE] Could not pass event PLAYER_JOIN to checkingame
java.lang.NullPointerException
	at me.empirebattles.checkingame.checkingamePlayerListener.onPlayerJoin(checkingamePlayerListener.java:56)
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:265)
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:58)
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:339)
	at net.minecraft.server.ServerConfigurationManager.c(ServerConfigurationManager.java:129)
	at net.minecraft.server.NetLoginHandler.b(NetLoginHandler.java:113)
	at net.minecraft.server.NetLoginHandler.a(NetLoginHandler.java:39)
	at net.minecraft.server.NetworkListenThread.a(SourceFile:94)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:527)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:425)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)