Make empty sets and maps size zero.
Make empty sets and maps size zero.

Changes the one use of wyt:by to match the old behavior.

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