List functionality generates invalid HTML

[leonardschoyen-at-dfo]

Steps to reproduce

1. Start unordered list.
2. Write "a", "b", and "c" on three items in the unordered list.
3. Put the cursor on the second line, behind the "b" text.
4. Increase the list level of the second line.
5. Inspect the generated HTML

Current behavior

The HTML that is generated currently look like this:

<ul class="UL">
    <li class="listItem">a</li>
    <ul class="UL">
        <li class="listItem">b</li>
    </ul>
    <li class="listItem">c</li>
</ul>

This HTML is invalid. There should only be <li> elements within <ul> and <ol>.

Expected behavior

The HTML that is generated should look like this:

<ul class="UL">
    <li class="listItem">
        a
        <ul class="UL">
            <li class="listItem">b</li>
        </ul>
    </li>
    <li class="listItem">c</li>
</ul>

The next level of the list, the inner <ul>, should be contained inside the <li> tag of the previous item, the one which contains "a".