Problem for closing markup

Hello, there is a markup validation problem :

Here’s my code :

<?php if (function_exists('vote_poll') && !in_pollarchive()): ?>
      <ul>
        <li><?php get_poll(2);?></li>
      </ul>
    <?php endif; ?>

And the output :

<ul>
<li><div id="polls-2" class="wp-polls">
	<form id="polls_form_2" class="wp-polls-form" action="/ashesheart/index.php" method="post">
		<p style="display: none;"><input type="hidden" id="poll_2_nonce" name="wp-polls-nonce" value="acd6e1074f" /></p>
		<p style="display: none;"><input type="hidden" name="poll_id" value="2" /></p>
		<h3 id="poll-question-2" class="poll-question">inFamous Second c'est</h3><div id="polls-2-ans" class="wp-polls-ans"><ul class="wp-polls-ul">
		</li>
<li><input type="radio" id="poll-answer-7" name="poll_2" value="7" /> <label for="poll-answer-7">Un très bon jeu</label></li>
<li><input type="radio" id="poll-answer-8" name="poll_2" value="8" /> <label for="poll-answer-8">Un jeu moyen</label></li>
<li><input type="radio" id="poll-answer-6" name="poll_2" value="6" /> <label for="poll-answer-6">Le meilleur jeu PS4</label></li>
<li><input type="radio" id="poll-answer-10" name="poll_2" value="10" /> <label for="poll-answer-10">Ne se prononce pas</label></li>
<li><input type="radio" id="poll-answer-9" name="poll_2" value="9" /> <label for="poll-answer-9">Pas intéressant du tout</label></li>
		<input id="vote-poll-button-2" type="button" name="vote" value="Voter" class="btn vote-poll-button" onclick="poll_vote(2);" />
	</form>
</div>

</ul>

There is the same markup closing problem when you’ve already vote (when there isn’t the form and the button).

https://ww.wp.xz.cn/plugins/wp-polls/