Describe the bug
When writing a nested list like this:

<ul>
  <li>List 1</li>
  <li>List 2
           <ul>
              <li>List 3</li>
              <li>List 4</li>
            </ul>
  </li>
</ul>

While the format is visually correct, the output HTML is incorrect and it's the following:

<ul>
  <li>List 1</li>
  <li>List 2</li>
  <li><ul><li>List 3</li></ul></li>
  <li><ul><li>List 4</li></ul></li>
  </li>
</ul>

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
The original HTML should be kept

Smartphone (please complete the following information):

• Device: iPhoneXs
• OS: iOS 12
• Version 1.5.1

Additional context
Add any other context about the problem here.