[gtk/wip/otte/for-master] stack: Make static analyzer happy

[Benjamin Otte <otte src gnome org>]

commit cda9007f0f12b1b436380e93d62b137862bbf3de
Author: Benjamin Otte <otte redhat com>
Date:   Fri Mar 6 05:56:29 2020 +0100

    stack: Make static analyzer happy

 gtk/gtkstack.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gtk/gtkstack.c b/gtk/gtkstack.c
index fc6a46347e..887c9cf6c9 100644
--- a/gtk/gtkstack.c
+++ b/gtk/gtkstack.c
@@ -1301,6 +1301,7 @@ stack_child_visibility_notify_cb (GObject    *obj,
   GtkStackPage *child_info;
 
   child_info = find_child_info_for_widget (stack, child);
+  g_return_if_fail (child_info != NULL);
 
   if (priv->visible_child == NULL &&
       gtk_widget_get_visible (child))