planning: fixed a bug when denominator could be zero
planning: fixed a bug when denominator could be zero

wanglei828/apollo,ycool/apollo,wanglei828/apollo,ApolloAuto/apollo,ApolloAuto/apollo,wanglei828/apollo,wanglei828/apollo,ApolloAuto/apollo,ApolloAuto/apollo,xiaoxq/apollo,jinghaomiao/apollo,jinghaomiao/apollo,xiaoxq/apollo,ycool/apollo,jinghaomiao/apollo,ycool/apollo,ApolloAuto/apollo,ycool/apollo,jinghaomiao/apollo,ycool/apollo,xiaoxq/apollo,jinghaomiao/apollo,xiaoxq/apollo,wanglei828/apollo,ycool/apollo,xiaoxq/apollo,ApolloAuto/apollo,jinghaomiao/apollo,xiaoxq/apollo,wanglei828/apollo