[Bug] the files function when called cannot get a file from input field

[otengkwame]

Inside the ci_core_helper.php the files function has a bug when called

// example when calling it in a controller
$avatar = files('avatar');

if ( ! function_exists('files')) 
{
    /**
     * function to get $_FILES values
     *
     * @param string $index
     * @return array|string
     */
    function files($index = '')
    {
        if ($index !== '') {
            return $_FILES[$index];
        }

        return $_FILES;
    }
}