input: Don't try to send pointer frames if no focus_client

Prevents a segfault when mousing into clients that don't get_pointer
like weston-simple-shm and weston-simple-damage.

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Marek Chalupa <mchqwerty@gmail.com>

src/input.c

@@ -390,6 +390,9 @@ weston_pointer_send_frame(struct weston_pointer *pointer)
 	struct wl_resource *resource;
 	struct wl_list *resource_list;
 
+	if (!pointer->focus_client)
+		return;
+
 	resource_list = &pointer->focus_client->pointer_resources;
 	wl_resource_for_each(resource, resource_list)
 		pointer_send_frame(resource);