shell: Set output on the focus_surfaces' view

Otherwise we crash when animating the view.

Signed-off-by: Emilio Pozuelo Monfort <emilio.pozuelo@collabora.co.uk>
diff --git a/src/shell.c b/src/shell.c
index 09ff86c..bf5c704 100644
--- a/src/shell.c
+++ b/src/shell.c
@@ -615,6 +615,7 @@
 	surface->configure_private = fsurf;
 
 	fsurf->view = weston_view_create (surface);
+	fsurf->view->output = output;
 
 	weston_view_configure(fsurf->view, output->x, output->y,
 				 output->width, output->height);