Large image not correct shown when there is only a small and medium image

[DrByte]

Or even better:

  // check for a large image else use medium else use small
  if (!file_exists(DIR_WS_IMAGES . 'large/' . $products_image_large)) {
    $products_image_large = $products_image_medium;
  } else {
    $products_image_large = DIR_WS_IMAGES . 'large/' . $products_image_large;
  }