Plugin Error

I am trying to update my PHP and the this plugin is throwing an error.

PHP Fatal error:  Uncaught Error: Undefined constant “css_form_id” in /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-content/plugins/styles-and-layouts-for-gravity-forms/display/class-fields-styles.php:282\nStack trace:\n#0 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-content/plugins/styles-and-layouts-for-gravity-forms/styles-layouts-gravity-forms.php(517): include()\n#1 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-includes/class-wp-hook.php(326): Gravity_customizer_admin->gform_enqueue_scripts()\n#2 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()\n#3 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-includes/plugin.php(517): WP_Hook->do_action()\n#4 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-content/plugins/gravityforms/gravityforms.php(7380): do_action()\n#5 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-content/plugins/gravityforms/form_display.php(3268): gf_do_action()\n#6 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-content/plugins/gravityforms/form_display.php(1230): GFFormDisplay::enqueue_form_scripts()\n#7 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-content/plugins/gravityforms/gravityforms.php(3660): GFFormDisplay::get_form()\n#8 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-content/plugins/gravityforms/gravityforms.php(2270): GFForms::get_form()\n#9 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-includes/shortcodes.php(434): GFForms::parse_shortcode()\n#10 [internal function]: do_shortcode_tag()\n#11 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-includes/shortcodes.php(273): preg_replace_callback()\n#12 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-content/plugins/popup-maker/classes/Helpers.php(22): do_shortcode()\n#13 /home/ljmlifei/domains/mymedicaresupplementplan.org/public_html/wp-include