Labels cannot be removed on editing

Where there is a Label field for Posts, labels cannot be removed after saving the post. When I try to edit the post, the labels cannot be removed by pressing 'Delete' or 'Backspace' buttons. Also, even if you untick the box of the label in the menu without adding any new labels the original label will not be removed. In summary, there does not seem to be anyway to remove labels you have added to the post, the only option is to change the label by unticking one label and ticking another one. 

NB: I'm on  UNA 12.0.0-RC1