[KPhotoAlbum] thumbnail build doesn't notice disk full

[Robert Krawitz]

   Date: Wed, 7 Nov 2007 17:26:31 -0500
   From: "Mark Eichin" <eichin at gmail.com>

   I haven't looked at the code but I'm guessing it's an artifact of
   the thumbnails being treated as a cache that doesn't *need* to work
   - but maintenance->build is an explicit request and shouldn't go
   that direction...

What happens if the thumbnail viewing code sees a zero-length
thumbnail file -- does it recreate the thumbnail, or does it blow up?
If the latter, then it's a bit more than just a cache!