Presence of unexpected numbered items next to headings in the generated HTML

Input: simple Microsoft Word document with numbered headings.

HTML generated by LibreOffice:

<ol>
    <li/>
        <h1>Heading 1</h1>
    <ol>
        <li/>
        <h2>Heading 2</h2>
    </ol>
</ol>

Issue: empty list items are inserted before each heading.