anchor.diff:  ThumbnailView.prototype.displayed_image_loaded_event = function(event)
   {
     /* If we don't have a loaded search, then we don't have any nearby posts to preload. */
  -  if(this.post_ids == null)
  +  if(this.post_ids === null || this.post_ids === undefined)
       return;
   
     var post_id = event.memo.post_id;
     var post_frame = event.memo.post_frame;
     var post_idx = this.get_post_idx([post_id, post_frame]);
  -  if(post_idx == null)
  +  if(post_idx === null || post_idx === undefined)
       return;
   
     /*
  
positive.code:   }
  
    var target = e.target;
    if(target.tagName == "INPUT" || target.tagName == "TEXTAREA")
      return false;
  
    if(key == 63) // ?, f
    {
      debug("xxx");
      document.fire("viewer:show-help");
  
negative.code: 
  ThumbnailView.prototype.remove_post = function(right)
  {
    if(this.posts_populated[0] === this.posts_populated[1])
      return false; /* none to remove */
  
    var node = this.container.down(".post-browser-posts");
  