code: protected void onBitmapNotAvailable(int position) {
          BitmapCache bc = cachedBitmaps.get(position);
          if (bc != null) {
              bc.status = SlideStatus.NOT_AVAILABLE;
              bc.bitmap = null;
          }
      }
docs: This function should be called by subclasses when they could not load a bitmap
  
  @param position the position of the item