fx: iterator: return NULL value if iterator status is not SUCCESS

fx/iterator.c

@@ -51,9 +51,8 @@ enum fx_status fx_iterator_move_next(const fx_iterator *it)
 {
 	enum fx_status status = FX_ERR_NOT_SUPPORTED;
 
-	fx_iterator_class *iface = fx_object_get_interface(
+	fx_iterator_class *iface
-		it,
+		= fx_object_get_interface(it, FX_TYPE_ITERATOR);
-		FX_TYPE_ITERATOR);
 	if (iface && iface->it_move_next) {
 		status = iface->it_move_next(it);
 	}
@@ -66,6 +65,10 @@ enum fx_status fx_iterator_move_next(const fx_iterator *it)
 
 const fx_value *fx_iterator_get_value(const fx_iterator *it)
 {
+	if (fx_iterator_get_status(it) != FX_SUCCESS) {
+		return NULL;
+	}
+
 	FX_CLASS_DISPATCH_VIRTUAL_0(
 		fx_iterator,
 		FX_TYPE_ITERATOR,
@@ -78,9 +81,8 @@ fx_status fx_iterator_erase(fx_iterator *it)
 {
 	enum fx_status status = FX_ERR_NOT_SUPPORTED;
 
-	fx_iterator_class *iface = fx_object_get_interface(
+	fx_iterator_class *iface
-		it,
+		= fx_object_get_interface(it, FX_TYPE_ITERATOR);
-		FX_TYPE_ITERATOR);
 	if (iface && iface->it_erase) {
 		status = iface->it_erase(it);
 	}