Description:
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when I use Blob to process gif animated picture (for example: 2 frames), getNumberImages can't get right value

Reproduce code:
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$file = '/path/to/animated/gif/picutre';

$foo = new Gmagick($file);

var_dump($foo->getNumberImages());

$bar = new Gmagick();

$bar->readImageBlob($foo->getImageBlob());

var_dump($bar->getNumberImages());

Expected result:
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int(2)
int(2)

Actual result:
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int(2)
int(1)