Maximize link on description mess up the editor

It's basically not possible to maximize the textarea of the description of an extension when editing it, without messing up the editor and risking to lose edition.

Reproduction step:

• Start editing an extension page
• Go to the textarea "Description" to edit it
• Click on the "maximize" edit link

Expected result:

• the textarea takes the full window and it's possible to exit the full screen and save the changes

Obtained result:

• the window only displays the top of the page, it's not possible to scroll anymore or to reach the description textarea, it's not possible to exit this view (see screenshot)

This bug has been reproduced first on extensions.xwiki.org
Note that it's possible to maximize the textarea for "source" and "general compatibility" but the bug happens for "description" and "custom install instructions".