Readers do not handle invalid images

[MisatoTremor]

When the readers create Drawing\Gd and use imagecreatefromstring with an unsupported or else invalid format it returns false. They then just pass this to setImageResource without verification. When getContents on these object is called (i.e. in a writer) it obviously can't return a valid image. Should this be fixed and if so, what would be the best way? Just don't create the shape at all?