‘wp_handle_upload’ filter should be treated as such (and not as action)

in Version 3.2.6 in upload.php on line 269:
do_action('wp_handle_upload', array('file' => $current_file, 'url' => wp_get_attachment_url($ID), 'type' => $new_filetype));

The ‘wp_handle_upload’ filter is not called as filter but called as an action.

This is important since the filter could actually change the filename, type and/or the url of the image (e.g. convert a bmp to jpg like imsanity or ewww image optimizer can do).

compare this to the original WordPress code in file.php:

	return apply_filters( 'wp_handle_upload', array(
		'file' => $new_file,
		'url'  => $url,
		'type' => $type
	), 'wp_handle_sideload' === $action ? 'sideload' : 'upload' );

or in functions.php:
return apply_filters( 'wp_handle_upload', array( 'file' => $new_file, 'url' => $url, 'type' => $wp_filetype['type'], 'error' => false ), 'sideload' );

this might also help solving the issue about PDF previews which I posted earlier today.