I've just created a test environment like what you described, and tried navigating between elements of the 2 templates in ERD dock window. I am getting NO Data displayed for items that doesn't resolve to any attributes like what you are expecting without any error dialogs. I am using ProcessBook 2012 though.
Not sure why you are getting the error, but I think this would require more troubleshooting of the error, looking at the configuration of the display and element etc. But I would say this probably would be better handled by Techsupport for further troubleshooting.