fix bug when taxon, strand, ref ifined without start/end attribute
fix bug when taxon, strand, ref ifined without start/end attribute

ofilangi/askomics,askomics/askomics,ofilangi/askomics,askomics/askomics,askomics/askomics,xgaia/askomics,ofilangi/askomics,xgaia/askomics,xgaia/askomics,ofilangi/askomics,xgaia/askomics,askomics/askomics