"Tips" panel can't be drag and dropped anymore

Steps to reproduce:

1. Go to "Administer Wiki"
2. Click on Look & Feel > Panels
3. Change the order of the panels from the right side with drag and drop
4. Click Save

Expected results: The order of the panels is changed according to the user actions.

Actual results: The Tips panel isn't drag-gable anymore. Also, when the user changes the order of the other 2 panels, some "undefined" appears under the "Panels displayed on the right" label, in the text field.