3rd level of hierarchy is generated incorrectly

3rd level tree:
```markdown
- a
  - b
    - c
```
is shown as 
```text
- a
  - b
  - c 
```
and generated as 
```
<li>
<p>a</p>
<ul>
<li>b</li>
<li>c</li>
</ul>
</li>
```
but 3rd level should be generated with extra `<ul>`/`</ul>` tag:
```
<li>a</li>
<ul><li>b</li>
    <ul><li>c</li></ul>
</ul>
```