If a Key button's Send Press To property is set to Linked Object, and the object specified in the Linked Object property does not exist, or is not a valid object for the Key button to work with, when the button is pressed, the application logs an error to the diagnostics.
For details on the error conditions that occur when a Key button function is sent to the selected object, see the help for the object you’re using the Key button with control list selectors and display list selectors.