function genesis_activate_fallback_theme( $stylesheet, WP_Theme $old_theme ) {

  unset( $_GET['activated'] ); // phpcs:ignore WordPress.Security.NonceVerification.Recommended

  if ( $old_theme->exists() && strpos( $old_theme->get_stylesheet(), 'genesis' ) === false ) {
    $fallback_stylesheet = $old_theme->get_stylesheet();
  } else {
    $default_theme       = WP_Theme::WP_Theme::get_core_default_theme();
    $fallback_stylesheet = $default_theme->get_stylesheet();
  }

  switch_theme( $fallback_stylesheet );
}