<?php
$aiosp_desc = get_post_meta($post->ID, _aioseop_description, true);
$aiosp_key = get_post_meta($post->ID, _aioseop_keywords, true);
?>

<?php if($aiosp_desc=='') : ?>
<meta name="description" content="" />
<?php endif; ?>
<? if($aiosp_key=='') : ?>
<meta name="keywords" content="" />
<?php endif; ?>