phppgadmin issue - blank fields

An issue with phppgadmin cropped up during the db work. If any field which is marked as a key of any type (even unique key) is NULL, clicking Edit next to a record opens the Edit form with all the fields blank - not filled in like in other cases. Does not happen for NULL fields when the fields are not marked as keys. It relates to the way the query is made in phppgadmin....