Carriage return in empty list leaves childless list behind.

[Alex T]

Steps to reproduce

1. Create an empty list

   <ul><li></li></ul>
   

2. Press enter when caret is inside the first empty list item (it should already be here)
3. Check the view source to see the current page source

Expected result

<p>&nbsp;</p>

Actual result

<p>&nbsp;</p>

<ul>
</ul>

The ul will be invisible as well, which is extra annoying.

Other details (browser, OS, CKEditor version, installed plugins)

I've tested this in both demo & nightly, on Chrome & Firefox.

[Jakub Ś]

Problem can be reproduced in all browsers starting from CKEditor 4.2.0.

Seems that version 4.2 has broken at least two things in empty lists #11897.