Comment 2 for bug 1670730

Object 39 is an image; but even Object 4 (the content stream of the first page; obj 93 *is* used on that page) has such a decompression error.

Ghostscript prints:
  warning: ignoring zlib error: incorrect data check

So probably libqpdf (which is used for the very low-level pdf stuff in pdftopdf) should also handle this as warning instead of as error?