Did you select the object to verify that it no longer has any inputs? If sourcing and executing don't work, then you could simply open the script in the script editor (or copy and paste it) and make a new shelf button with just the commands inside the script. All the script does is duplicates the selected object without inputs, deletes the old object, and then renames the new object with the old object's name. It happens very fast, so it might seem nothing happened.