OceanWP child theme error

Undefined variable: output_custom_css - /wp-content/themes/oceanwp/functions.php:693
#10 /wp-includes/class-wp-hook.php:286 - OCEANWP_Theme_Class::save_customizer_css_in_file('/* General CSS...')
#9 /wp-includes/class-wp-hook.php:310 - WP_Hook->apply_filters('', Array[1])
#8 /wp-includes/plugin.php:453 - WP_Hook->do_action(Array[1])
#7 /wp-includes/class-wp-admin-bar.php:80 - do_action('admin_bar_init...')
#6 /wp-includes/admin-bar.php:47 - WP_Admin_Bar->initialize()
#5 /wp-includes/class-wp-hook.php:286 - _wp_admin_bar_init('')
#4 /wp-includes/class-wp-hook.php:310 - WP_Hook->apply_filters(NULL, Array[1])
#3 /wp-includes/plugin.php:453 - WP_Hook->do_action(Array[1])
#2 /wp-admin/admin.php:156 - do_action('admin_init')
#1 /wp-admin/themes.php:10 - require_once('/var/www/vhost...')