Fatal error: Uncaught Error: Class "RWMB_Helpers_String" not found in /var/www/wp-content/plugins/meta-box/inc/functions.php:290
Stack trace:
#0 /var/www/wp-content/plugins/meta-box/inc/core.php(26): rwmb_get_registry('meta_box')
#1 /var/www/wp-includes/class-wp-hook.php(324): RWMB_Core->register_meta_boxes('')
#2 /var/www/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)
#3 /var/www/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#4 /var/www/wp-settings.php(700): do_action('init')
#5 /var/www/wp-config.php(104): require_once('/var/www/wp-set...')
#6 /var/www/wp-load.php(50): require_once('/var/www/wp-con...')
#7 /var/www/wp-blog-header.php(13): require_once('/var/www/wp-loa...')
#8 /var/www/index.php(17): require('/var/www/wp-blo...')
#9 {main}
thrown in /var/www/wp-content/plugins/meta-box/inc/functions.php on line 290