improves u3r_mug_bytes() efficiency (a little)
improves u3r_mug_bytes() efficiency (a little)

ngzax/urbit,ngzax/urbit,urbit/urbit,jfranklin9000/urbit,urbit/urbit,jfranklin9000/urbit,jfranklin9000/urbit,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,urbit/urbit,jfranklin9000/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit