This fixes issues that snuck in in the latest update which caused errors when trying to use the plugin on older servers which don't have certain API methods (especially 1.8.8). Please note that some features might not work fully on such old versions (e.g. offhand display) ‒ especially as Mojang continues adds even more capabilities to the base game ‒ and I would urge everyone to update to a modern version if in any way possible.