well, I could not get it to work, but I noticed that when you just remove the code for the error, zenphoto just loads the gallery page. To me this is better than getting a white error page with no navigation to anywhere... I'm wondering if it's "bad" to do without the zen error by deleting 'echo "\n[b]".gettext(" Error:[/b] the requested object was not found. Please go back and try again.");
'`echo "\n<!-- The requested object (album=\"" . $album . "\": image=\"" . $image . "\") was not found. -->";
exit();`'