fixes +spin to preserve the type of the head of the product
fixes +spin to preserve the type of the head of the product

urbit/urbit,urbit/urbit,jfranklin9000/urbit,jfranklin9000/urbit,urbit/urbit,jfranklin9000/urbit,belisarius222/arvo,urbit/urbit,urbit/urbit,jfranklin9000/urbit,cgyarvin/arvo,joemfb/arvo,ngzax/urbit,cgyarvin/arvo,jfranklin9000/urbit,joemfb/arvo,urbit/urbit,belisarius222/arvo,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit