WordPress数据库错误MySQL服务器已离开查询SELECT

使用wordpress多站点，当试图剪切主题时，得到了以下错误日志：

WordPress database error MySQL server has gone away for query SELECT option_value FROM tblog_c4c.wp_6010_options WHERE option_name = 'post_count' LIMIT 1 made by do_action('customize_controls_enqueue_scripts'), call_user_func_array, WP_Customize_Widgets->enqueue_scripts, WP_Customize_Widgets->get_available_widgets, WP_Customize_Widgets->get_widget_control, call_user_func_array, wp_widget_control, call_user_func_array, WP_Widget->form_callback, NLposts_Widget->form, get_blog_details, get_option, m_wpdb->query

浏览器显示504 Gateway Time-out

已经增加了时间限制：

set_time_limit(0);

ini_set('mysql.connect_timeout', '0');

ini_set('max_execution_time', '0');

有什么解决办法吗？