fix eyre ++back rev-0 beak
fix eyre ++back rev-0 beak

casting to and from %hiss was failing due to occuring at a null revision

ngzax/urbit,ohAitch/arvo,ohAitch/arvo,joemfb/arvo,belisarius222/arvo,ngzax/urbit,jfranklin9000/urbit,cgyarvin/arvo,urbit/urbit,urbit/urbit,cgyarvin/arvo,jfranklin9000/urbit,ngzax/urbit,solri/arvo,jfranklin9000/urbit,jfranklin9000/urbit,belisarius222/arvo,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,Fang-/arvo,ngzax/urbit,jfranklin9000/urbit,urbit/urbit,urbit/urbit,jfranklin9000/urbit,urbit/urbit,urbit/urbit,eglaysher/arvo,ngzax/urbit,joemfb/arvo,ngzax/urbit