Avoid 404s on empty month views (TEC 3.0)

/**
 * Let's set up a filter than transforms the status of month views from 404 (if a given
 * month happens to be devoid of events) to 200.
 */
add_filter('status_header', 'avoid_tribe_month_view_404s');

function avoid_tribe_month_view_404s($status) {
    global $wp_query;

    if ( ! isset($wp_query->query_vars['eventDisplay'])
        || 'month' !== $wp_query->query_vars['eventDisplay']
        || false === strpos($status, '404 Not Found') )
            return $status;

    $wp_query->is_404 = false;
    return str_replace('404 Not Found', '200 OK', $status);
}