Without the patch, media-type of cover-image in OEBPS/content.opf is empty.
(found with epub validator)
Change-Id: I74c8098d4cbbedcd899fdc473e485724e66a4dd1
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/205721
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>
Tested-by: Julien Nabet <serval2412@yahoo.fr>
(cherry picked from commit c9df26ea09)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/205735
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
Tested-by: Jenkins