Please describe the problem:
The top of the side panel contains a minor drawing error that's triggered in new
windows when the side panel is not expanded. It's illustrated in the attached
pictures.

Steps to reproduce:
1. Open a new window with the side panel _not_ expanded (see p1.png). Notice the
drawing error that's highlighted with red in p1.png
2. Expand the side panel (p2.png)
3. Hide it again (p3.png) and notice the drawing error is gone.


Actual results:
The drawing error is removed.

Expected results:
The drawing error shouldn't have been there in the first place.

Does this happen every time?
Yes.

Other information:
I'm using ubuntu dapper.