Facebook graph API can't break down by asset

Question

I'm trying to get a breakdown at image and video asset level with Facebook graph API, but whenever I add image_asset or video_asset the response becomes empty, is there anything I am doing wrong or is there some API limitation I should know about? I can't find anything in the docs:

With country breakdown it works fine but when I switch to image_asset or video_asset I get a response like this:

    {
        "data": []
    }