{use $node, $pres}
{if str_trim( format_text( $pres, $node->nodeValue ) ) == ''}
<img src="/qrcode.php?d=http://derickrethans.nl/talks.html"/>
{else}
<img src="/qrcode.php?d={raw format_text( $pres, $node->nodeValue )}"/>
{/if}