Bukkit

What is the issue?
I'm having problems with the "/skyblock delete" command, not so much the "delete" part, but the part, where you have to type "/skyblock yes" after, it gives me an error: "An internal error occurred while attempting to perform this command"

And it's the same problem with deleting party, and from the admin commands!

Please provide any additional information below.
Here is the log that comes up when I do it!:
[INFO] (user) issued server command: /skyblock delete
[INFO] (user) issued server command: /skyblock yes
[SERVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'skyblock' in plugin SkyBlockCo-Op v1.5