album thumbnail doesn't display if the thumbnail is from an album

I just installed 5.x-1.x-dev from Nov 1 and noticed that the album thumbnail isn't displaying of the thumbnail is from a child album. I have a some albums that only contain other albums and there is no option to set the thumbnail for these to anything other than random.

I worked around this in _acidfree_get_album_thumb() by making a recursive call if the thumbnail we are returning is an album. Patch included.

if ($thumb->type == 'acidfree') {
$thumb = _acidfree_get_album_thumb($thumb);
}