[gtk+] wayland: Never send NULL app id

[Timm Bäder <baedert src gnome org>]

commit dfc7a531dbf9210557ca1b1879bee6dcf038d901
Author: Timm Bäder <mail baedert org>
Date:   Fri Nov 17 20:07:18 2017 +0100

    wayland: Never send NULL app id
    
    The old gdk_get_program_class was never returning NULL, but
    g_get_prgname might. So use the same fallback app id name we were using
    before.

 gdk/wayland/gdkwindow-wayland.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gdk/wayland/gdkwindow-wayland.c b/gdk/wayland/gdkwindow-wayland.c
index 1ae53ad..224c642 100644
--- a/gdk/wayland/gdkwindow-wayland.c
+++ b/gdk/wayland/gdkwindow-wayland.c
@@ -1473,6 +1473,9 @@ gdk_wayland_window_create_xdg_toplevel (GdkWindow *window)
 
   app_id = g_get_prgname ();
 
+  if (app_id == NULL)
+    app_id = "GTK+ Application";
+
   zxdg_toplevel_v6_set_app_id (impl->display_server.xdg_toplevel, app_id);
 
   maybe_set_gtk_surface_dbus_properties (window);