Added additional an empty html comment when convert html to markdown!

[mrhdias]

Every time that I run this code to convert html to markdown an empty html additional comment is added to result.

const converter = new showdown.Converter();
console.log(converter.makeMarkdown(`<h1 id="test">Test1</h1>
<h2 id="test2">Test2</h2>
<ol>
<li>abc</li>
<li>def</li>
<li>ghi</li>
</ol>
<p>Test3</p>`));

Output:

# Test1

## Test2

1. abc
2. def
3. ghi

<!-- --> <===== Aditional empty comment

Test3