Deleting a sub bullet, deletes entire bullet list

[sanil]

Steps to reproduce:

1) Create a Bullet list

2) Add a Sub bullet

3) Select the sub bullet and press backspace

Entire bullet list gets removed

[sanil]

Here is a screencast ​http://screencast.com/t/xqkEYkekllz

[Jakub Ś]

Problem can be reproduced in all browsers from CKEditor 4.0 (works fine in 3.x and 4.0 Beta).