CKEditor mangles an internal link that is removed via the 'Remove' button in the link picker dialog

When an internal link is removed via the 'Remove' button in the link picker dialog, it's href attribute changes to "http://" instead.

Steps to reproduce:
1. login to the archetype CMS
2. edit a document
3. add an internal link
4. double-click the added internal link to re-open the link picker dialog
5. click the 'Remove' button

Expected: the added link is removed again
Actual: the link stays and is changed to <a href="http://">, resulting in an odd broken link in the front-end.

Workaround: remove the link via the 'remove link' button in the CKEditor toolbar instead.