cleaning up my Aperture library

My Aperture library tends to grow much larger than it should. It seems as though Aperture does not delete the thumbnails for photographs even when deleting the originals, leaving several gigabytes of orphaned kruft behind, accumulating bits, filling up volumes. I delete most of the photos I shoot, so the majority of thumbnails in my library are orphaned. But there’s a quick and easy way to clean i...