Weird "function()…" message instead of success text

If WP_DEBUG in wp-config.php is set to true and you use the plugin, there is a weird message with some code instead of success text:

function () { if (c) { var a = c.length; n(arguments), j ? (l...

The regeneration works fine, only the message is bad. Taking a look at the JSON result reveals, it has the success JSON but is prepended with a php notice:

<b>Notice</b>: Undefined variable: regenerate_status in <b>/var/.../wp-content/plugins/regenerate-thumbnails/regenerate-thumbnails.php</b> on line <b>498</b><br />

Obviously $regenerate_status is never initialized or set but still used in line 498.

Please fix, thanks.

http://wordpress.org/extend/plugins/force-regenerate-thumbnails/