Next and Prev post link breaks code on last post

This should work. Wasn’t closed well

<div id="cooler-nav" class="navigation">
    <div class="wpb_wrapper">
        <h3>More Underwater Media</h3>
    </div>


<?php $prevPost = get_previous_post(true);
    if($prevPost) {?>
        <div class="nav-box previous">
            <div class="navig_thumb_wrapper">
                <?php $prevthumbnail = get_the_post_thumbnail($prevPost->ID, array(100,100) );?>
                <?php previous_post_link('%link',"$prevthumbnail", TRUE); ?>
            </div>
                <?php previous_post_link('%link',"<p>< %title</p>", TRUE); ?>

        </div>
<?php } ?>



<?php  $nextPost = get_next_post(true);
    if($nextPost) {?>
        <div class="nav-box next" style="float:right;">
            <div class="navig_thumb_wrapper">
                <?php $nextthumbnail = get_the_post_thumbnail($nextPost->ID, array(100,100) );?>
                <?php next_post_link('%link',"$nextthumbnail", TRUE); ?>
            </div>
                <?php next_post_link('%link',"<p>%title ></p>", TRUE); ?>

        </div>

<?php } ?>

</div>