freiden

Thanks Dulabs for the help.

To fix this error use this code below
global $wp_version;

if(!(function_exists('get_user_to_edit'))){
    require_once(ABSPATH.'/wp-includes/user.php');
    require_once(ABSPATH.'/wp-admin/includes/user.php');
    require_once(ABSPATH.'/wp-includes/registration.php');
}

That should fix it!