Description:
------------
get the favicon from http://www.jetphotos.net/favicon.ico and save it to disk

then, use this sample code to convert it to png, there is no error or exception, but the png output contains nothing

tried to run identify -verbose favicon.ico and did not get any error output, did convert favicon.ico favicon.png and there is no error either, it is just the png output cannot be displayed

somehow firefox can display the favicon, try go to http://www.jetphotos.net and favicon is shown next to the address, safari cannot display the favicon though

Reproduce code:
---------------
<?php
try
{
$im = new Imagick();
$im->setFormat('ico');
$im->readImageBlob(file_get_contents('favicon.ico'));
$im->flattenImages();
$im->setFormat('png');

$data = $im->getImageBlob();
header('Content-Type: image/png');
header('Content-Length: ' . strlen($data));
echo $data;
}
catch (Exception $ex)
{
    header('Content-Type: text/plain');
    $output = 'exception happened';
    header('Content-Length: ' . strlen($output));
    echo $output;
}
?>

Expected result:
----------------
if the original ico image has errors, Imagick or ImageMagick should return error or Exception

Actual result:
--------------
conversion to PNG is successful, but the result is a blank or non-displayable image