[gtk] icontheme: Annotate return value as nullable

[Timm Bäder <baedert src gnome org>]

commit eeec6f8fb985ec8d14d11e3a114ea597918564e9
Author: Timm Bäder <mail baedert org>
Date:   Sat Aug 31 10:46:06 2019 +0200

    icontheme: Annotate return value as nullable

 gtk/gtkicontheme.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkicontheme.c b/gtk/gtkicontheme.c
index b8d3b9a5e2..a6916d1d29 100644
--- a/gtk/gtkicontheme.c
+++ b/gtk/gtkicontheme.c
@@ -4456,7 +4456,8 @@ gtk_icon_theme_lookup_symbolic_colors (GtkCssStyle *style,
  *
  * See gtk_icon_info_load_symbolic() for more details.
  *
- * Returns: (transfer full): a #GdkPixbuf representing the loaded icon
+ * Returns: (transfer full) (nullable): a #GdkPixbuf representing the loaded icon
+ *   or %NULL If the icon could not be loaded
  */
 GdkPaintable *
 gtk_icon_info_load_symbolic_for_context (GtkIconInfo      *icon_info,