A malformed PDF may store a non-dictionary object (an array, name, or
other type) at /Resources or /Resources /XObject. The pdfinfo image
scanner iterated these with .items()/.as_dict() and probed them with the
`in` operator, which raise TypeError/ValueError on non-dictionary pikepdf
objects and crashed PdfInfo on otherwise-processable files. OCRmyPDF's
domain is messy, machine-generated PDFs, so scanning must tolerate this.
Guard _image_xobjects and _find_form_xobject_images with
isinstance(x, Dictionary) before iterating, treating a non-dictionary
/Resources or /XObject as "no image XObjects". This is the same
robustness class as the pdfa.py find_nonembedded_cid_fonts fix, applied
to the pdfinfo image scanner.
James R. Barlow
b60df59c62