custom fields error if blank

Hi – I’ve a custom field column2 in pages.php. It works ok, but if the field is blank for certain pages where not required it gives and error in page.php – syntax wrong in this ?

<?php $custom_fields = get_post_custom();
$my_custom_field = $custom_fields[‘column2’];
foreach ( $my_custom_field as $key => $value )
echo “”.$value.””; ?>