Fatal error about wp_install_maybe_enable_pretty_permalinks()

Hi,

I want to add a new database table. so I use

require( ABSPATH . 'wp-admin/includes/upgrade.php' );

        if ($wpdb->get_var("SHOW TABLES LIKE '$new_uam_table'") != $new_uam_table) {
            $sql = "CREATE TABLE IF NOT EXISTS ".$new_uam_table." (
                <code>ID</code> int(11) NOT NULL AUTO_INCREMENT,
                <code>groupname</code> tinytext NOT NULL,
                <code>groupdesc</code> text NOT NULL,
                <code>read_access</code> tinytext NOT NULL,
                <code>write_access</code> tinytext NOT NULL,
                <code>ip_range</code> mediumtext NULL,
                PRIMARY KEY  (<code>ID</code>)
            ) ".  $snxCharsetCollate .";";
            dbDelta($sql);
        }

When I activated my plugin, it got a fatal error:

Plugin could not be activated because it triggered a fatal error.

Fatal error: Cannot redeclare wp_install_maybe_enable_pretty_permalinks() (previously declared in /home/www/wordpress/wp-admin/includes/upgrade.php:279) in /home/www/wordpress/wp-admin/includes/upgrade.php on line 347

I believe the function “wp_install_maybe_enable_pretty_permalinks()” should be included in

if ( !function_exists('wp_install_maybe_enable_pretty_permalinks') ) :
function wp_install_maybe_enable_pretty_permalinks() {...}
endif;