DBTreeList properties don't display checkboxes in edit mode and layout is broken on flamingo

I noticed the bug on a 6.2.2 instance, I didn't test how old the bug is.
It concerns the db tree list property in edit mode.

Add a property of type database tree list in a class, and make a request that points it to a documents hierarchy (I used a hierarchy created with http://extensions.xwiki.org/xwiki/bin/view/Extension/Classification+Application ) . First you will hit XWIKI-8760 (depending on your hierarchy, because it's a matter of parents). If you hit it, put the attached treeview in your skin and continue. Then, the result will be as such:

• on flamingo skin, the tree is unreadable, the layout is completely broken (and no checkboxes are displayed)
• on colibri skin, the tree is a little better but still no checkboxes.