invalid ui-icon PNGs in download builds

As of 1.8rc3, the http://jqueryui.com/download page creates builds with invalid PNG images.

If I select the Humanity theme and select the following Components:

• Core
• Widget
• Mouse
• Position
• Draggable
• Resizable
• Dialog
• Tabs

the following files are invalid in the /css/humanity/images/ directory of the resulting jquery-ui-1.8rc3.custom.zip file:

{{{

$ cat ui-icons_f08000_256x240.png

<br />

<b>Fatal error</b>: Call to undefined function ImageColorMatch() in

<b>/srv/jqueryui.com/htdocs/themeroller/images/phpthumb.filters.php</b>

on line <b>1040</b><br />

$ cat ui-icons_f35f07_256x240.png

<br />

<b>Fatal error</b>: Call to undefined function ImageColorMatch() in

<b>/srv/jqueryui.com/htdocs/themeroller/images/phpthumb.filters.php</b>

on line <b>1040</b><br />

$ cat ui-icons_ff7519_256x240.png

<br />

<b>Fatal error</b>: Call to undefined function ImageColorMatch() in

<b>/srv/jqueryui.com/htdocs/themeroller/images/phpthumb.filters.php</b>

on line <b>1040</b><br />

$ cat ui-icons_ffffff_256x240.png

<br />

<b>Fatal error</b>: Call to undefined function ImageColorMatch() in

<b>/srv/jqueryui.com/htdocs/themeroller/images/phpthumb.filters.php</b>

on line <b>1040</b><br />