alert pop up required when removing relationship

When removing a relationship (like relationship between a doctor and patient) , a reason is required to remove the relationship . If the reason is not provided , neither the relationship is removed nor any notification is given . If the user clicks on the remove button ( with reason being null ) , then an alert pop up (asking the user to provide a reason ) must be displayed .
Example url (relationship between users - haryy 8787 potter and Johnstone Chebochok Laboso ) -http://demo.openmrs.org/openmrs/patientDashboard.form?patientId=9355&causeOfDeathOther=