QTextDocument::toHtml: nested lists (ul, ol) not nested in output

Nested lists in QTextDocument don't always appear as nested in QTextDocument::toHtml output.

Sample:

  <ul>
    <li>item-1</li>
    <li>item-2
    <ul>
      <li>item-2.1</li>
    </ul>
    </li>
  </ul>

which would appear as something along the lines in QTextDocument::toHtml output:

<ul>
  <li>item-1</li>
  <li>item-2</li>
</ul>
<ul>
  <li>item-2.1</li>
</ul> 

NOTE: If there was another list item before the closing tag of the first ul in the sample html above, the problem would not occur.

Steps to reproduce the issue:

1. Run the attached project
2. Compare the output with the input html