Bukkit

What steps will reproduce the problem?
1. Absolutely no idea what caused it.

What is the expected output? What do you see instead?
N/A

What version of the product are you using?
AncientGates v1.8

Do you have an error log of what happened?
http://pastebin.com/PaaQG1Rn

Please provide any additional information below.
N/A

Well this is a odd one!

The error suggests that whilst a player was moving, they moved to a location that had no block associated with it :/ i.e. the player wasn't even standing in air (as even air is a block).

Perhaps this is a spigot/craftbukkit bug? Keep your spigot up-to-date and keep an eye out for this error as you keep updating.

There's nothing much I can do with this. All locations should have a block associated with them :/.

@peewi96: Go

It was very odd when I encountered it as well, It appeared to of occurred with some other plugin errors when the users was kicked for Internal exception.

Spigot is always fully up to date as well as all my other plugins.