I managed to stop the above Error log generating by commenting out the following line in /includes/modules/sideboxes/reviews_scrolling.php.

Code:
//    if (isset($_GET['products_id'])) {  $scrolling_review .= " and p.products_id = '" . (int)$_GET['products_id'] . "'";  }
The scrolling review box still seems to work fine, not sure if this was the correct way to stop that error log or if doing this will effect any other function on my website?!

Hope someone can confirm