Disguise

I want to disguise my mob into my skin but this is what i get:

[19:42:59 WARN]: java.lang.NullPointerException
[19:42:59 WARN]: at me.libraryaddict.disguise.disguisetypes.Disguise.createDisguise(Disguise.java:92)
[19:42:59 WARN]: at me.libraryaddict.disguise.disguisetypes.MobDisguise.<init>(MobDisguise.java:29)
[19:42:59 WARN]: at io.lumine.xikage.mythicmobs.compatibility.LibsDisguisesSupport.setDisguise(LibsDisguisesSupport.java:542)
[19:42:59 WARN]: at...

Disguise