unnecessary h1 when using horizontal rules to create new slide

[yihui]

suppose this is test.md

% title
% author

# first slide

asdf

---

second slide

I run pandoc -s -t dzslides test.md -o test.html and will get:

<section>
  <h1 class="title">title</h1>
  <h2 class="author">author</h2>
  <h3 class="date"></h3>
</section>
<section class="slide level1" id="first-slide">
<h1 id="first-slide">first slide</h1>
<p>asdf</p>
</section>
<section class="slide level1" id="section">
<h1 id="section"></h1>
<p>second slide</p>
</section>

Note the second slide has an empty heading <h1 id="section"></h1>, and I guess this should not have been generated because I do not really have a heading for this slide. Sometimes I just want to show an image or blockquote in a slide.

I'm using v1.9.1.1 under Ubuntu.