Upgrade player on tag combiner pages

e.g. http://www.theguardian.com/fashion+type/video

The player doesn't get upgraded because `app.js` crashes when trying to load `media.js` bootstrap. This fixes it, although perhaps we should use a better default value than an empty string here.
Without a `contentType`, tracking will break

If there's no `contentType` on the page object, can we try an infer it from the url