[mutter] build: Fix non-wayland builds

[Ting-Wei Lan <lantw src gnome org>]

commit 6cc48d8cbbf11fa82ec78cac0b29d52f05eabb60
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Sun Dec 24 17:55:14 2017 +0800

    build: Fix non-wayland builds
    
    meta_dnd_wayland_handle_end_modal is not available on non-wayland build.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=791916

 src/compositor/compositor.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index 51d22bc..aa49347 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -419,11 +419,13 @@ meta_end_modal_for_plugin (MetaCompositor *compositor,
   meta_backend_ungrab_device (backend, META_VIRTUAL_CORE_POINTER_ID, timestamp);
   meta_backend_ungrab_device (backend, META_VIRTUAL_CORE_KEYBOARD_ID, timestamp);
 
+#ifdef HAVE_WAYLAND
   if (meta_is_wayland_compositor ())
     {
       meta_dnd_wayland_handle_end_modal (compositor);
       meta_display_sync_wayland_input_focus (display);
     }
+#endif
 }
 
 static void