[gobject-introspection] Add missing nullable annotation to g_object_info_get_parent

[Christoph Reiter <creiter src gnome org>]

commit f9a92fc3a4d380b4795eefda593082779763d792
Author: Jonne Haß <me jhass eu>
Date:   Thu May 14 17:26:21 2020 +0200

    Add missing nullable annotation to g_object_info_get_parent

 girepository/giobjectinfo.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/girepository/giobjectinfo.c b/girepository/giobjectinfo.c
index efb9ad76..3f3423cc 100644
--- a/girepository/giobjectinfo.c
+++ b/girepository/giobjectinfo.c
@@ -89,7 +89,7 @@ g_object_info_get_field_offset (GIObjectInfo *info,
  *
  * Obtain the parent of the object type.
  *
- * Returns: (transfer full): the #GIObjectInfo. Free the struct by calling
+ * Returns: (transfer full) (nullable): the #GIObjectInfo. Free the struct by calling
  * g_base_info_unref() when done.
  */
 GIObjectInfo *