Fixes check of ticks in stddev, now that __len__ has been removed.
Fixes check of ticks in stddev, now that __len__ has been removed.

magne-max/zipline-ja,morrisonwudi/zipline,MonoCloud/zipline,kmather73/zipline,davidastephens/zipline,magne-max/zipline-ja,enigmampc/catalyst,AlirezaShahabi/zipline,grundgruen/zipline,humdings/zipline,joequant/zipline,mattcaldwell/zipline,CDSFinance/zipline,dmitriz/zipline,stkubr/zipline,florentchandelier/zipline,DVegaCapital/zipline,StratsOn/zipline,michaeljohnbennett/zipline,bartosh/zipline,humdings/zipline,semio/zipline,joequant/zipline,jimgoo/zipline-fork,sketchytechky/zipline,DVegaCapital/zipline,erikness/AlephOne,otmaneJai/Zipline,wilsonkichoi/zipline,StratsOn/zipline,mattcaldwell/zipline,bartosh/zipline,dkushner/zipline,erikness/AlephOne,umuzungu/zipline,grundgruen/zipline,jimgoo/zipline-fork,chrjxj/zipline,semio/zipline,CarterBain/AlephNull,wilsonkichoi/zipline,CarterBain/AlephNull,YuepengGuo/zipline,keir-rex/zipline,iamkingmaker/zipline,gwulfs/zipline,nborggren/zipline,euri10/zipline,ChinaQuants/zipline,dhruvparamhans/zipline,ronalcc/zipline,wubr2000/zipline,quantopian/zipline,otmaneJai/Zipline,jordancheah/zipline,quantopian/zipline,YuepengGuo/zipline,jordancheah/zipline,MonoCloud/zipline,enigmampc/catalyst,morrisonwudi/zipline,wubr2000/zipline,cmorgan/zipline,aajtodd/zipline,florentchandelier/zipline,ronalcc/zipline,zhoulingjun/zipline,dhruvparamhans/zipline,umuzungu/zipline,dmitriz/zipline,AlirezaShahabi/zipline,alphaBenj/zipline,Scapogo/zipline,zhoulingjun/zipline,euri10/zipline,Scapogo/zipline,davidastephens/zipline,nborggren/zipline,dkushner/zipline,stkubr/zipline,cmorgan/zipline,sketchytechky/zipline,kmather73/zipline,aajtodd/zipline,iamkingmaker/zipline,michaeljohnbennett/zipline,alphaBenj/zipline,gwulfs/zipline,ChinaQuants/zipline,CDSFinance/zipline,keir-rex/zipline,chrjxj/zipline