Fix the exclude nullable field workaround for 1.7+
Fix the exclude nullable field workaround for 1.7+

wangjun/djangae,trik/djangae,jscissr/djangae,martinogden/djangae,wangjun/djangae,pablorecio/djangae,kirberich/djangae,grzes/djangae,leekchan/djangae,wangjun/djangae,chargrizzle/djangae,kirberich/djangae,armirusco/djangae,grzes/djangae,SiPiggles/djangae,nealedj/djangae,asendecka/djangae,jscissr/djangae,chargrizzle/djangae,asendecka/djangae,leekchan/djangae,grzes/djangae,pablorecio/djangae,jscissr/djangae,leekchan/djangae,stucox/djangae,stucox/djangae,armirusco/djangae,martinogden/djangae,trik/djangae,trik/djangae,nealedj/djangae,SiPiggles/djangae,pablorecio/djangae,armirusco/djangae,potatolondon/djangae,martinogden/djangae,nealedj/djangae,kirberich/djangae,SiPiggles/djangae,chargrizzle/djangae,stucox/djangae,asendecka/djangae,potatolondon/djangae