The easiest way would be to add a simple conditional:
$values = get_post_custom_values("listing_heading_10");
if ( $values ) { ?>
<h3 class="listing-title"><?php echo $values[0]; ?></h3>
<?php }
That said, is there any reason that you can’t put your output code in a foreach
loop?
e.g.
$values = get_post_custom_values( 'some_value' );
foreach ( $values as $value ) {
// echo output content here
}
It may be helpful to put your custom meta values into an array, to facilitate looping through them if they exist. So, instead of:
$values = get_post_custom_values("listing_heading_10")
…you could have:
$values get_post_custom_values( 'listing_heading' )
And instead of
$values
…you could output:
$values[10]
etc.