[gtk+] Window: Do not connect to NULL screen in init()

[Daniel Boles <dboles src gnome org>]

commit 6984d0847b7e70bc7108c7b298bab1c85e708f7c
Author: Daniel Boles <dboles src gnome org>
Date:   Thu Aug 31 20:19:58 2017 +0100

    Window: Do not connect to NULL screen in init()
    
    Do not connect to get_settings_for_screen() if we have no screen…
    
    Use g_signal_connect(), not connect_object(), to match how set_screen()
    makes this same connection, and how finalize() already disconnects it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=705640

 gtk/gtkwindow.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index a6b64d8..2e8f5b4 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -1858,9 +1858,10 @@ gtk_window_init (GtkWindow *window)
   gtk_window_update_debugging ();
 
 #ifdef GDK_WINDOWING_X11
-  g_signal_connect_object (gtk_settings_get_for_screen (priv->screen),
-                           "notify::gtk-application-prefer-dark-theme",
-                           G_CALLBACK (gtk_window_on_theme_variant_changed), window, 0);
+  if (priv->screen)
+    g_signal_connect (gtk_settings_get_for_screen (priv->screen),
+                      "notify::gtk-application-prefer-dark-theme",
+                      G_CALLBACK (gtk_window_on_theme_variant_changed), window);
 #endif
 
   widget_node = gtk_widget_get_css_node (GTK_WIDGET (window));