PHP fatal error with version 1.0.68

Hi there,

Thank you for taken a look at the issue:
https://ww.wp.xz.cn/support/topic/server-fs_method-php-fatal-error/

However the version 1.0.68 has another similar php fatal error and crashed the site:

PHP Fatal error: Uncaught TypeError: ftp_nlist(): Argument #1 ($ftp) must be of type resource, null given in /wp-admin/incl udes/class-wp-filesystem-ftpext.php:420\nStack trace:\n#0 /wp-admin/includes/class-wp-filesystem-ftpext.php(420): ftp_nlist()\n#1 /plugin/seo-by-rank-math/includes/modules/robots-txt/class-robots-txt.php(94): WP_Filesystem_FTPext->exists()\n#2 /plugin/seo-by-rank-math/includes/modules/robots-txt/options.php(14): RankMath\\Robots_Txt::get_robots_data()\ n#3 /plugin/seo-by-rank-math/includes/admin/class-options.php(168): include('...')\n#4 /wp-includes/class-wp-hook.php(292) : RankMath\\Admin\\Options->register_option_page()\n#5 /wp-includes/class-wp-hook.php(316): WP_Hook->apply_filters()\n#6 /wp-includes/plugin.php(484): WP_Hook->do_action()\n#7 /plugin/seo-by-rank-math/vendor/cmb2/cmb2/bootstrap.php(26): do_action()\n#8 /plugin/seo-by-rank-math/vendor/cmb2/cmb2/init.php(165): cmb2_bootstrap ()\n#9 /wp-includes/class-wp-hook.php(292): CMB2_Bootstrap_290->include_cmb()\n#10 /wp-includes/class-wp-hook.php(316): WP_Hook->apply_filters()\n#11 /wp-includes/plugin.php(484): WP_Hook->do_action()\n#12 /wp-settings.php(560): do_action()\n#13 /wp-config.php(100): require_once('...')\n#14 /wp-load.php(37): require_once('...')\n#15 /wp-admin/admin.php(34): require_once('...')\n#16 /wp-admin/update-core.php(10): require_once('...')\n#17 {main}\n thrown in /wp-admin/includes/class-wp-filesystem-ftpext.php on line 420

Please see if this can be solved, thank you for your assistance!

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