Put a check on the InventoryClickEvent to ensure it's a player inv being clicked

Forgot to check for null in the InventoryClickEvent, fixed that.

Edited to make it work back to 1.14

Added permission based slot limits. So if your server global config limit is 5, and you really wanna stick it to some group lol, you can give that group or user the permission deathinvlimiter.slotlimits.# where # is a number 0 to 36. This will override the global config setting.

You can now use * as the player when you do /dilimit player to set slot counts. So like if you wanted to lift everyone's slot restrictions at once, /dilimit player * 0 would do it.