Plugin Help PickaxeSell console error help!

Hello so ive been on a prison server called 'Epsilon Prison' and they had a plugin that did so when u right click a pickaxe it sells your stuff from a mine

Code:
http://pastebin.com/TjaCTnEW

Plugin.yml:
http://pastebin.com/dMNEpWVu

Extra: Yes i know that it says MAIN.MAIN in plugin.yml but let me say something it works

The problem is that an error comes up in console

Sorry but that doesn't work @Konato_K.
We tried this with NMS at 2 ticks delay and it works sometimes at different computers.
I think the client can only set walking speed if he changed the world successfully.

https://bukkit.atlassian.net/browse/BUKKIT-2419

I found a interesting issue on attlasian.

 

@T0X1C0801
You cannot use == in combination with ItemStacks, use .isSimiliar for example, however once the durability of your Pickaxe changes, this is not going to work.
In case you want to ignore the durability simply compare the Material using
e.getItemInHand().getType.equals(Material.DIAMOND_PICKAXE)

 

@mrCookieSlime

Still didn't work but now ive learned something about durability tho it still comes with like spigot 1567 error (i think it was) but just asking do u know if i can do this with autosell?