BUG Empty positions in extract_pos showed up as nans. Replace with 0s.
BUG Empty positions in extract_pos showed up as nans. Replace with 0s.

ChinaQuants/pyfolio,YihaoLu/pyfolio,dursk/pyfolio,chayapan/pyfolio,ChinaQuants/pyfolio,quantopian/pyfolio,YihaoLu/pyfolio,quantopian/pyfolio,femtotrader/pyfolio,dursk/pyfolio,femtotrader/pyfolio