Pressing ENTER over a list item not only creates a new li, but also inserts additional <br> element.

Video: https://www.screencast.com/t/PZcYTKEtY4v

Steps to reproduce:
1. Open in Chrome:
2. Switch to Html mode and insert the following content:
<ol>
    <li>123 456
    <ol>
        <li>abc</li>
    </ol>
    </li>
    <li>789</li>
</ol>

3. Switch to design mode
4. Put the cursor inside the first li (e.g. before 5) and press ENTER

Result: A <br> element is added in the beginning of the new <li> element