Changes in bullet list for those wanting short explanation.

• Fix NPE
• Made Vault 100% optional

So this finally fixes the NPE error that could happen in only 1.9 up when a player who has no item in the main hand but has an item in offhand. So turns out the real problem was me coding at the 1.8 API I've now updated to 1.11 API so I need people to verify that the wand still works in 1.8. Also in this update, I made the economy completely optional as I forgot to update the sign method so now setting Cost to 0 will disable the need for Vault. As always please leave a review and considering donating. If you find bugs report them.