Query fails with an empty gallery using Postgres

Postgres cannot take a null value when checking against an integer, such as looking for the latest image in a gallery when there are no images in the gallery. This problem can be traced to line 378 in image.module with the line $albums[$i]->latest = node_load(array('nid' => $last->nid));

A check to see if there is even an image returned should be done to make sure there are no errors in Postgres. I propose the following to replace that line:

if (isset($last->nid)) {
  $albums[$i]->latest = node_load(array('nid' => $last->nid));
}

I have tested it on a prototype site running under Postgres and have no problems so far and it fixes the problem.