needed to deal with the case where there's no profitable dev
needed to deal with the case where there's no profitable dev

tests caught the case that no profitable dev would cause an error.  just return an empty dataframe in this case

UDST/urbansim,apdjustino/urbansim,AZMAG/urbansim,ual/urbansim,SANDAG/urbansim,AZMAG/urbansim,SANDAG/urbansim,synthicity/urbansim,synthicity/urbansim,synthicity/urbansim,ual/urbansim,AZMAG/urbansim,SANDAG/urbansim,UDST/urbansim,AZMAG/urbansim,ual/urbansim,synthicity/urbansim,ual/urbansim,apdjustino/urbansim,UDST/urbansim,UDST/urbansim,apdjustino/urbansim,apdjustino/urbansim,SANDAG/urbansim