[gnome-shell] Add missing allow-none for set_style_pseudo_class

[Colin Walters <walters src gnome org>]

commit 37a948e4eb3c2b8f012550b5f2d93c5a8b7cd2a4
Author: Colin Walters <walters verbum org>
Date:   Fri Oct 23 15:40:09 2009 -0400

    Add missing allow-none for set_style_pseudo_class
    
    https://bugzilla.gnome.org/show_bug.cgi?id=599442

 src/st/st-widget.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/st/st-widget.c b/src/st/st-widget.c
index 2570ac6..c2488ec 100644
--- a/src/st/st-widget.c
+++ b/src/st/st-widget.c
@@ -1052,7 +1052,7 @@ st_widget_get_style_pseudo_class (StWidget *actor)
 /**
  * st_widget_set_style_pseudo_class:
  * @actor: a #StWidget
- * @pseudo_class: a new pseudo class string
+ * @pseudo_class: (allow-none): a new pseudo class string
  *
  * Set the style pseudo class
  */