Fix crash when sort_order is None
Fix crash when sort_order is None

Toshakins/wagtail,mixxorz/wagtail,jnns/wagtail,iansprice/wagtail,mikedingjan/wagtail,torchbox/wagtail,takeflight/wagtail,kaedroho/wagtail,nealtodd/wagtail,mikedingjan/wagtail,kaedroho/wagtail,rsalmaso/wagtail,nutztherookie/wagtail,jnns/wagtail,zerolab/wagtail,gasman/wagtail,jnns/wagtail,iansprice/wagtail,FlipperPA/wagtail,zerolab/wagtail,zerolab/wagtail,nealtodd/wagtail,rsalmaso/wagtail,nimasmi/wagtail,mikedingjan/wagtail,wagtail/wagtail,rsalmaso/wagtail,thenewguy/wagtail,FlipperPA/wagtail,timorieber/wagtail,mixxorz/wagtail,timorieber/wagtail,iansprice/wagtail,thenewguy/wagtail,mixxorz/wagtail,nutztherookie/wagtail,jnns/wagtail,gasman/wagtail,gasman/wagtail,FlipperPA/wagtail,torchbox/wagtail,Toshakins/wagtail,wagtail/wagtail,nutztherookie/wagtail,kaedroho/wagtail,takeflight/wagtail,timorieber/wagtail,nealtodd/wagtail,nutztherookie/wagtail,wagtail/wagtail,wagtail/wagtail,kaedroho/wagtail,nimasmi/wagtail,Toshakins/wagtail,thenewguy/wagtail,gasman/wagtail,nimasmi/wagtail,thenewguy/wagtail,FlipperPA/wagtail,timorieber/wagtail,torchbox/wagtail,Toshakins/wagtail,wagtail/wagtail,thenewguy/wagtail,nimasmi/wagtail,gasman/wagtail,mixxorz/wagtail,zerolab/wagtail,nealtodd/wagtail,mixxorz/wagtail,rsalmaso/wagtail,zerolab/wagtail,kaedroho/wagtail,takeflight/wagtail,rsalmaso/wagtail,iansprice/wagtail,torchbox/wagtail,takeflight/wagtail,mikedingjan/wagtail