StatsLoginError

[18:36:39 ERROR]: Could not pass event PlayerLoginEvent to Achievements v2.0.0-50
org.bukkit.event.EventException
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:305) ~[spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.PlayerList.attemptLogin(PlayerList.java:453) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.LoginListener.b(LoginListener.java:118) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.LoginListener.c(LoginListener.java:54) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.NetworkManager.a(NetworkManager.java:231) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.ServerConnection.c(ServerConnection.java:148) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.MinecraftServer.A(MinecraftServer.java:809) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.DedicatedServer.A(DedicatedServer.java:368) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.MinecraftServer.z(MinecraftServer.java:651) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at net.minecraft.server.v1_8_R2.MinecraftServer.run(MinecraftServer.java:554) [spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_31]
Caused by: java.lang.IllegalArgumentException: The validated object is null
	at org.apache.commons.lang.Validate.notNull(Validate.java:192) ~[spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at org.apache.commons.lang.Validate.notNull(Validate.java:178) ~[spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	at nl.lolmewn.stats.player.UUIDPlayerManager.findPlayer(UUIDPlayerManager.java:89) ~[?:?]
	at nl.lolmewn.stats.api.StatsAPI.getPlayer(StatsAPI.java:365) ~[?:?]
	at nl.lolmewn.stats.api.StatsAPI.getPlayerId(StatsAPI.java:440) ~[?:?]
	at nl.lolmewn.achievements.player.PlayerManager.loadPlayer(PlayerManager.java:51) ~[?:?]
	at nl.lolmewn.achievements.EventListener.onLogin(EventListener.java:79) ~[?:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_31]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_31]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_31]
	at java.lang.reflect.Method.invoke(Method.java:483) ~[?:1.8.0_31]
	at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301) ~[spigot-1.8.3.jar:git-Spigot-2f787bd-501372f]
	... 13 more