Happened when the doc was smaller than 1024 bytes.

Change-Id: Ie5eea5905a09722e7958495d26e6c78ee234d3ba
Reviewed-on: https://gerrit.libreoffice.org/31500Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>