Crash on admin page after updating to 3.8.6 and 3.8.7

Hi, admin page is not working after updating to versions 3.8.6 and 3.8.7. This is what appears on the apache log:

AH01071: Got error 'PHP message: PHP Fatal error:  Uncaught TypeError: ftp_fput(): Argument #1 ($ftp) must be of type FTP\\Connection, null given in /home/beta/www/wp-admin/includes/class-wp-filesystem-ftpext.php:212\nStack trace:\n#0 /home/beta/www/wp-admin/includes/class-wp-filesystem-ftpext.php(212): ftp_fput()\n#1 /home/beta/www/wp-content/plugins/master-slider/admin/includes/msp-admin-functions.php(98): WP_Filesystem_FTPext->put_contents()\n#2 /home/beta/www/wp-content/plugins/master-slider/admin/class-master-slider-admin.php(126): msp_save_custom_styles()\n#3 /home/beta/www/wp-content/plugins/master-slider/admin/class-master-slider-admin.php(112): Master_Slider_Admin->after_plugin_update()\n#4 /home/beta/www/wp-includes/class-wp-hook.php(308): Master_Slider_Admin->admin_init()\n#5 /home/beta/www/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()\n#6 /home/beta/www/wp-includes/plugin.php(517): WP_Hook->do_action()\n#7 /home/beta/www/wp-admin/admin.php(175): do_action()\n#8 /home/beta/www/wp-admin/index.php(10): r...', referer:

Reverting back to 3.8.5 via FTP upload fixes it.