Description:
------------
This script results in the error message:
'http://leopold.sage.wisc.edu/world.vis.675.gd2' is not a 
valid GD2 file

But it *is* valid. The problem is that the parameter passed 
has zero width, but the error message is misleading.

Reproduce code:
---------------
<?php
$img = imagecreatefromgd2part('http://leopold.sage.wisc.edu/world.vis.675.gd2', 0, 100,0, 100);

/* This works fine:
$img = imagecreatefromgd2part('http://leopold.sage.wisc.edu/world.vis.675.gd2', 0, 100,100, 100);
*/

header('Content-Type: image/png');
imagepng($img);
?>