fix rub to crash gracefully upon decoding invalid data
fix rub to crash gracefully upon decoding invalid data

if we exceed the number of available bits, crash.

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