[gtk+] GtkFlowBox: Add missing nullable annotation

[Timm Bäder <baedert src gnome org>]

commit c3fd1b3b73747d6451f5c531384044bcdd676199
Author: Timm Bäder <mail baedert org>
Date:   Thu Dec 10 16:54:59 2015 +0100

    GtkFlowBox: Add missing nullable annotation

 gtk/gtkflowbox.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkflowbox.c b/gtk/gtkflowbox.c
index 775d0a0..3d1a076 100644
--- a/gtk/gtkflowbox.c
+++ b/gtk/gtkflowbox.c
@@ -4214,8 +4214,9 @@ gtk_flow_box_insert (GtkFlowBox *box,
  *
  * Gets the nth child in the @box.
  *
- * Returns: (transfer none): the child widget, which will
- *     always be a #GtkFlowBoxChild
+ * Returns: (transfer none) (nullable): the child widget, which will
+ *     always be a #GtkFlowBoxChild or %NULL in case no child widget
+ *     with the given index exists.
  *
  * Since: 3.12
  */