[empathy] Don't crash in window_get_workspace under Wayland

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 942395f7b81e4a81922c8bcb1c11f9676d32f3f8
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Sat Jan 16 00:20:15 2016 -0600

    Don't crash in window_get_workspace under Wayland

 libempathy-gtk/empathy-ui-utils.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/libempathy-gtk/empathy-ui-utils.c b/libempathy-gtk/empathy-ui-utils.c
index fb080ce..e662c69 100644
--- a/libempathy-gtk/empathy-ui-utils.c
+++ b/libempathy-gtk/empathy-ui-utils.c
@@ -1122,6 +1122,8 @@ out:
   g_free (cmd);
 }
 
+#ifdef GDK_WINDOWING_X11
+
 /* Most of the workspace manipulation code has been copied from libwnck
  * Copyright (C) 2001 Havoc Pennington
  * Copyright (C) 2005-2007 Vincent Untz
@@ -1213,18 +1215,24 @@ window_get_workspace (Screen *xscreen,
   return number;
 }
 
+#endif
+
 /* Ask X to move to the desktop on which @window currently is
  * and the present @window. */
 void
 empathy_move_to_window_desktop (GtkWindow *window,
     guint32 timestamp)
 {
+#ifdef GDK_WINDOWING_X11
   GdkScreen *screen;
   Screen *xscreen;
   GdkWindow *gdk_window;
   int workspace;
 
   screen = gtk_window_get_screen (window);
+  if (!GDK_IS_X11_SCREEN (screen))
+    goto out;
+
   xscreen = gdk_x11_screen_get_xscreen (screen);
   gdk_window = gtk_widget_get_window (GTK_WIDGET (window));
 
@@ -1237,6 +1245,7 @@ empathy_move_to_window_desktop (GtkWindow *window,
 
 out:
   gtk_window_present_with_time (window, timestamp);
+#endif
 }
 
 void