//Option 1 (with a default if sidebar isnt available)
<?php if (!function_exists('dynamic_sidebar') || !dynamic_sidebar('topright')) { ?>
<?php } else { ?>
Put something here if you want something to display by default.
<?php } ?>

//Option 2: It can look like this if you dont have a default:
<?php if (!function_exists('dynamic_sidebar') || !dynamic_sidebar('topright')) { ?>
<?php } ?>