Problem description: Using a list style which has its numbering for some level in set to "none" and then  promoting or demoting to that level in the "Bullets and Numbering" toolbox makes this toolbox disappear, with no way of further changing the level (other than, applying a different list style, where the numbering of said level is not set to "none"). 

Steps to reproduce:
1. Press F11 to bring up the "Styles and Formatting" pane.
2. Go to "List Styles" and modify, say, List 1.
3. Go to the "options" tab and select, say, level 2.
4. In the "Numbering" box select none and click ok.
5. Write some text and apply the "List 1" list style to it; the "Bullets and Numbering" toolbox should appear.
6. Demote your text one level (to level 2); the bullet disappears (as intended) but also the "Bullets and Numbering" toolbox (not intended, as now there is no convenient way to make further changes to the list, like promotion/demotion, etc).

Expected behavior: The "Bullets and Numbering" toolbox should stay open regardless of the type of numbering used in some level of a list style.

Platform: Windows XP SP3