Error creating thumbnail: convert: improper image header `/var/www/wiki.documentfoundation.org/images/0/0d/10_20_releases_multiversion.xcf' @ error/xcf.c/ReadXCFImage/1316. convert: no images defined `/var/www/wiki.documentfoundation.org/images/tmp/transform_34ccb4b633c0.png' @ error/convert.c/ConvertImageCommand/3229. Error code: 1