[07:31:34 ERROR]: Could not pass event PlayerJoinEvent to MapSwitcher v1.0
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:310) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerList.onPlayerJoin(PlayerList.java:298) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.PlayerList.a(PlayerList.java:157) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.LoginListener.b(LoginListener.java:144) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.LoginListener.c(LoginListener.java:54) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.NetworkManager.a(NetworkManager.java:231) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.ServerConnection.c(ServerConnection.java:148) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:814) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_111]
Caused by: java.lang.IllegalArgumentException: Name cannot be null
        at org.apache.commons.lang.Validate.notNull(Validate.java:192) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.craftbukkit.v1_8_R3.CraftServer.getWorld(CraftServer.java:1014) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at org.bukkit.Bukkit.getWorld(Bukkit.java:496) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        at net.Floxiii.MapSwitcher.JoinListener.onJoin(JoinListener.java:25) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_111]
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_111]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_111]
        at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_111]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot-1.8.8-R0.1-SNAPSHOT-latest.jar:git-Spigot-db6de12-18fbb24]
        ... 14 more