When doing this manipulation :
- connect on a server with 'referral' set to 'manage'
- select an entry which is a referral
- right click on 'new entry'
- add an entry (for instance, with OC = person, sn=test, cn=test)
- when the popup with the proposed referral is showed, just click on cancel
- an empty error popup appears. Clicking on 'Details' gives :