Fix Err fallout for graph/iterator.HasA iterator

graph/iterator/hasa_iterator.go

@@ -51,6 +51,7 @@ type HasA struct {
 	dir       quad.Direction
 	resultIt  graph.Iterator
 	result    graph.Value
+	err       error
 	runstats  graph.IteratorStats
 }
 
@@ -202,6 +203,9 @@ func (it *HasA) Next() bool {
 	it.resultIt = &Null{}
 
 	if !graph.Next(it.primaryIt) {
+		if err := graph.Err(it.primaryIt); err != nil {
+			it.err = err
+		}
 		return graph.NextLogOut(it, 0, false)
 	}
 	tID := it.primaryIt.Result()
@@ -210,6 +214,10 @@ func (it *HasA) Next() bool {
 	return graph.NextLogOut(it, val, true)
 }
 
+func (it *HasA) Err() error {
+	return it.err
+}
+
 func (it *HasA) Result() graph.Value {
 	return it.result
 }