Search in Relationships (and maybe other parts) returns wrong results after using ajax

If you use the ajax search for relationships to select one of the contacts and then change your mind and type in something completely different, you still get the result you picked first.

to reproduce:
1. to do a record on the demo site
2. go to relationships, select "sibling of"
3. type in "smith" and select one of the many records
4. delete the field again and type something else in there
5. without selecting a contact, hit "enter" or "search"
6. you get the contact selected in point 3 as only result