An extra checkbox is generated for list with checkbox if it mixes with empty lines

[tomyeh]

markdownToHtml('''
- [ ] A
-
- [ ] B''',
blockSyntaxes: [const OrderedListWithCheckboxSyntax(), UnorderedListWithCheckboxSyntax()]);

<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox"></input>A</li>
<li class="task-list-item"><input type="checkbox"></input></li>
<li class="task-list-item"><input type="checkbox"></input>B</li>
</ul>

It works fine if it is not empty. For example,

- [ ] A
- C
- [ ] B