Expend-button doesn't work well in Quick watch tooltips.

Steps:
1. Go-> preference->Debugger->General, check use "tooltips in main editor when debugging".
2. Start Debug a Qt Gui application or use the attachments.
3. Cursor Stay at on parameter "*argv[ ] ",there will be a Quick watch window shown.
4. Click expend-button in front of this parameter ,the second line shown
5. Click expend-button in front of second line.

Expected result:
The third line should be shown.

Actually result:.
After click it ,The third line dosen't shown,and the second line disappear.