FQL event pic_cover returns null

Question

I am trying to fetch the cover picture for a public event on Facebook, but the pic_cover field returns null.

Here is the event: https://www.facebook.com/events/545127275518406/

Here is my FQL query: SELECT pic_cover FROM event WHERE eid=545127275518406

That query returns:

{
  "data": [
    {
      "pic_cover": null
    }
  ]
}

Another public event (https://www.facebook.com/events/133752506800219/) using the same query (with substituted eid) returns:

{
  "data": [
    {
      "pic_cover": {
        "cover_id": 431180503630072, 
        "source": "https://sphotos-a.xx.fbcdn.net/hphotos-ash4/299824_431180503630072_82863704_n.jpg", 
        "offset_y": 36
      }
    }
  ]
}

Why does the first event return null if it does have a cover image?

Answer 1

Asking the user the permission for user_photos partially solves this issue. I say partially because some photoes are not returned. Bear in mind that pic_cover and pic_big are two different things