Added missing check for image_type (https://oss-fuzz.com/v2/testcase-detail/4973962497884160).
Added missing check for image_type (https://oss-fuzz.com/v2/testcase-detail/4973962497884160).

Danack/ImageMagick,Danack/ImageMagick,Danack/ImageMagick,Danack/ImageMagick,Danack/ImageMagick,Danack/ImageMagick