Additional instances of autocalculated NPCs do not get autocalculated spells

Should be a regression from https://github.com/OpenMW/openmw/pull/2954

To reproduce, visit Ginith Ancestral Tomb. Tredere Llaren should be there and she should know the Burden spell. If you then spawn a second instance of the same NPC, that NPC won't know the spell. GetSpell burden faithfully reports this.