[gtk] assistant: Fix a refcounting oversight

[Matthias Clasen <matthiasc src gnome org>]

commit c16a861f6811ef3c2013101694f80107422912d1
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Feb 8 09:49:54 2019 -0500

    assistant: Fix a refcounting oversight
    
    The assistant needs to hold a ref on the pages.

 gtk/gtkassistant.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkassistant.c b/gtk/gtkassistant.c
index 12c38ea43f..f20bbe0428 100644
--- a/gtk/gtkassistant.c
+++ b/gtk/gtkassistant.c
@@ -1773,6 +1773,8 @@ gtk_assistant_insert_page (GtkAssistant *assistant,
   page_info->has_padding = TRUE;
 
   return gtk_assistant_add_page (assistant, page_info, position);
+
+  g_object_unref (page_info);
 }
 
 static int
@@ -1815,7 +1817,7 @@ gtk_assistant_add_page (GtkAssistant *assistant,
   if (position < 0 || position > n_pages)
     position = n_pages;
 
-  priv->pages = g_list_insert (priv->pages, page_info, position);
+  priv->pages = g_list_insert (priv->pages, g_object_ref (page_info), position);
 
   if (position == 0)
     sibling = NULL;