Bukkit

What steps will reproduce the problem?
1. Create and link the new overworld and the new End world.

Overworld Case:
2. Find an end portal or use "/setblock ~ ~-1 ~ end_portal" command.
3. Try to go to the portal.

The End case:
4. Go to the End.
5. Defeat the End dragon or use "/setblock ~ ~-1 ~ end_portal" command.
6. Go to the portal, and you'll end up in the nether portal of the overworld.

What is the expected output? What do you see instead?
Overworld Case:
The expected case is to go to the platform in the End. The actual outcome is... a bunch of errors generating for every tick the player is in the end portal block.

End Case:
The expected case is to get to the spawn point or the bed on the Overworld. The actual outcome is it leads to the nether portal in the Overworld.

What version of the product are you using?
Latest Spigot and MW 5.2.8

What version of the craftbukkit/bukkit are you using?
Spigot 1.9.

Do you have an error log of what happened?
Overworld case:
[00:03:16] [Server thread/INFO]: [MultiWorld] [PortalHandler] got portal 1 for location -263.27335845947533,67.41999998688698,229.725905424037.
[00:03:16] [Server thread/ERROR]: Could not pass event PlayerPortalEvent to MultiWorld v5.2.8
org.bukkit.event.EventException
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:310) ~[spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:502) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:487) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.PlayerList.changeDimension(PlayerList.java:728) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.EntityPlayer.c(EntityPlayer.java:537) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.BlockEnderPortal.a(BlockEnderPortal.java:45) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.Entity.checkBlockCollisions(Entity.java:839) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.Entity.move(Entity.java:473) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.PlayerConnection.a(PlayerConnection.java:542) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.PacketPlayInFlying.a(SourceFile:126) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.PacketPlayInFlying$PacketPlayInPosition.a(SourceFile:57) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.PlayerConnectionUtils$1.run(SourceFile:13) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_73]
    at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_73]
    at net.minecraft.server.v1_9_R1.SystemUtils.a(SourceFile:45) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.MinecraftServer.D(MinecraftServer.java:721) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.DedicatedServer.D(DedicatedServer.java:400) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.MinecraftServer.C(MinecraftServer.java:660) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:559) [spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at java.lang.Thread.run(Unknown Source) [?:1.8.0_73]
Caused by: java.lang.IllegalArgumentException: Cannot use null location!
    at com.google.common.base.Preconditions.checkArgument(Preconditions.java:125) ~[spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at org.bukkit.event.player.PlayerMoveEvent.validateLocation(PlayerMoveEvent.java:91) ~[spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at org.bukkit.event.player.PlayerMoveEvent.setTo(PlayerMoveEvent.java:86) ~[spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    at multiworld.addons.NetherPortalHandler.onPlayerPortal(NetherPortalHandler.java:41) ~[?:?]
    at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source) ~[?:?]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_73]
    at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_73]
    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot-1.9.jar:git-Spigot-2038f4a-fc9ee90]
    ... 20 more

The End case:
[00:05:12] [Server thread/INFO]: [MultiWorld] [PortalHandler] got portal 1 for location -13.424259261276354,62.53584062504456,26.548685870559254.
[00:05:12] [Server thread/INFO]: [MultiWorld] [PortalHandler] got PortalType.END.
[00:05:13] [Server thread/INFO]: [MultiWorld] [PortalHandler] [PortalType.END] used for entity player to get to world stuff
[00:05:13] [Server thread/INFO]: [MultiWorld] [PortalHandler] got portal 1 for location -13.424259261276354,62.53584062504456,26.548685870559254.
[00:05:14] [Server thread/WARN]: SimonOrJ moved too quickly! -235.57574073872365,5.464159374955443,197.45131412944073

Please provide the result of /mw debug below:
[00:03:24] [Server thread/INFO]: [MultiWorld] Now printing debug information
[00:03:24] [Server thread/INFO]: [MultiWorld] MultiWorld version: 5.2.8
[00:03:24] [Server thread/INFO]: [MultiWorld] Bukkit version: git-Spigot-2038f4a-fc9ee90 (MC: 1.9)
[00:03:24] [Server thread/INFO]: [MultiWorld] 
[00:03:24] [Server thread/INFO]: [MultiWorld] --<[Modules]>--
[00:03:24] [Server thread/INFO]: [MultiWorld] [State, pluginName]
[00:03:24] [Server thread/INFO]: [MultiWorld] [Working, EndPortalHandler]
[00:03:24] [Server thread/INFO]: [MultiWorld] [Unloaded, EnderChestBlokker]
[00:03:24] [Server thread/INFO]: [MultiWorld] [Unloaded, WorldChatSeperatorPlugin]
[00:03:24] [Server thread/INFO]: [MultiWorld] [Unloaded, GameModeChancer]
[00:03:24] [Server thread/INFO]: [MultiWorld] [Working, WorldSpawnHandler]
[00:03:24] [Server thread/INFO]: [MultiWorld] [Working, NetherPortalHandler]
[00:03:24] [Server thread/INFO]: [MultiWorld] 
[00:03:24] [Server thread/INFO]: [MultiWorld] --<[CommandStacks]>--
[00:03:24] [Server thread/INFO]: [MultiWorld] multiworld.command.DefaultCommandStack
[00:03:24] [Server thread/INFO]: [MultiWorld]  - /mw []
[00:03:24] [Server thread/INFO]: [MultiWorld] multiworld.command.DefaultCommandStack
[00:03:24] [Server thread/INFO]: [MultiWorld]  - /mw [debug]