If/Else on Repeatable Groups

I want to link to each speaker’s Twitter, but not all speakers have them. This code below shows the link for all speakers if one speaker has a twitter account and doesn’t show it for any if none do.

I need to figure out how to show the link to twitter for those that only have a twitter account.

<?php if ($speaker['speakers_twitter'][1] !=='') { ?>
<li><a href="http://www.twitter.com/<?php echo $speaker['speakers_twitter'][1]; ?>">@<?php echo $speaker['speakers_twitter'][1]; ?></a></li>
<?php } ?>

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