Prevent nulls from entering the OPML
Prevent nulls from entering the OPML

closes #297

elancom/goread,lnmx/goread,youprofit/goread,Feitianyuan/goread,elancom/goread,beni55/goread,mikecb/goread,P7h/goread,lnmx/goread,mjibson/goread,doublehou/goread,Feitianyuan/goread,youprofit/goread,mikecb/goread,elancom/goread,mgaitan/goread,P7h/goread,mgaitan/goread,youprofit/goread,doublehou/goread,wangjun/goread,wangjun/goread,mjibson/goread,lnmx/goread,beni55/goread,Feitianyuan/goread,mjibson/goread,mikecb/goread,P7h/goread,doublehou/goread,beni55/goread,mgaitan/goread,wangjun/goread