Fatal error: Uncaught TypeError: Return value of NF_Admin_Metaboxes_Calculations::registerReactMetabox() must be an instance of void, none returned in /home/bosscafe/ftp/serwisekspresow/wp-content/plugins/ninja-forms/includes/Admin/Metaboxes/Calculations.php:37 Stack trace: #0 /home/bosscafe/ftp/serwisekspresow/wp-content/plugins/ninja-forms/includes/Admin/Metaboxes/Calculations.php(7): NF_Admin_Metaboxes_Calculations->registerReactMetabox() #1 /home/bosscafe/ftp/serwisekspresow/wp-content/plugins/ninja-forms/ninja-forms.php(367): NF_Admin_Metaboxes_Calculations->__construct() #2 /home/bosscafe/ftp/serwisekspresow/wp-content/plugins/ninja-forms/ninja-forms.php(1152): Ninja_Forms::instance() #3 /home/bosscafe/ftp/serwisekspresow/wp-content/plugins/ninja-forms/ninja-forms.php(1155): Ninja_Forms() #4 /home/bosscafe/ftp/serwisekspresow/wp-settings.php(462): include_once('/home/bosscafe/...') #5 /home/bosscafe/ftp/serwisekspresow/wp-config.php(89): require_once('/home/bosscafe/...') #6 /home/bosscafe/ftp/serwisekspresow/wp-loa in /home/bosscafe/ftp/serwisekspresow/wp-content/plugins/ninja-forms/includes/Admin/Metaboxes/Calculations.php on line 37