coalesceImages doesn't work properly with some animated gifs

[Godefroy]

Hi,

I encountered a bug in coalesceImages with some animated gifs. No problem with Imagick.

Here is my test code:

$image = new Gmagick();
$image->readImageBlob($object->getData());
if($image->getNumberImages() > 1){
    $image = $image->coalesceImages();
    do {
        $frame = $image->current();
        $frame->cropThumbnailImage($width, $height);
        $frame->setCompressionQuality(85);
    }while($image->nextImage());
    $image = $image->deconstructimages();

}else{
    $image->cropThumbnailImage($width, $height);
    $image->setCompressionQuality(85);
}
echo $image->getImagesBlob();

And here is an image for test:

(sorry, I randomly picked an image from a blog)

If I try to crop it with $width=400 and $height=400:

[Danack]

Trying to investigate this issue leads to a segfault:

$width = 50;
$height = 50;

$image = new Gmagick("./testGif.gif");
$image = $image->coalesceImages();

do {
    $frame = $image->current();
    $frame->cropThumbnailImage($width, $height);
    $frame->setCompressionQuality(85);
} 
while($image->nextImage());

$image = $image->deconstructimages();
$image->writeImages("./output.gif");

==20240== Invalid read of size 8
==20240==    at 0xC8AE26A: zim_gmagick_deconstructimages (gmagick_methods.c:706)
==20240==    by 0x601997: ZEND_DO_FCALL_SPEC_HANDLER (zend_vm_execute.h:842)
==20240==    by 0x5CB52F: execute_ex (zend_vm_execute.h:417)
==20240==    by 0x61BB32: zend_execute (zend_vm_execute.h:458)
==20240==    by 0x58DF26: zend_execute_scripts (zend.c:1428)
==20240==    by 0x5326B7: php_execute_script (main.c:2471)
==20240==    by 0x61FBE0: do_cli (php_cli.c:974)
==20240==    by 0x620305: main (php_cli.c:1345)
==20240==  Address 0x0 is not stack'd, malloc'd or (recently) free'd