Fix media object featuring for visualizations

Addresses #1712

The problem was that clicking the radio button would send a JSON object containing the string 'undefined' instead of 'project', and it would send back the giant red screen of death instead of valid JSON.  The meida object box's JS was looking for an attribute 'type' on a div that wasn't there, and was sending undefined instead.  I think this came about during the recent push to have HTML that's actually valid, seeing how a 'type' attributed on a div is super invalid.