A bulleted list in Writer is terminated by inserting an empty item (i.e.,
pressing Enter twice), while the behaviour is different in Impress.

Steps to reproduce:
1. Open Writer and create a new empty document.
2. Format -> Bullets and Numbering -> Select a bullet -> OK
3. Insert some items, then press Enter twice. The list is terminated.
4. Open Impress and create a new empty document.
5. Select a format "Title, text"
6. Insert some items in the bulleted list, press Enter twice

Expected:
7. List is terminated.

Actual:
7. Empty items are added and insertion in list continues.

[Reported by tiziana Ferro during Italian QA tests]