As a Wikisource user, I want the PDF issue with displaying images to be fixed, so that I can 1) download books as PDFs with 1) proper image display, and 2) no errors.
Background: Wikisource users have let us know that they experience the following issue: "For me, the most frustrating problem while exporting an ebook in "pdf" format, in most cases (see for example for the book https://fr.wikisource.org/wiki/Le_Lorgnon_(Scribe), the image on the cover page does not appear, and an error message can be seen when opening the file (in french "Données insuffisantes pour une image" => trad. : insuffient data for an image)." They say this issue started around February 2020.
**Acceptance Criteria:**
* Investigate issue of cover page images not appearing in PDF exports
* Investigate issue of error messages appearing when trying to open PDF exports