Apparently the offset needs to be checked against the total size
of the stream, not against the remaining size.

(regression from b67d9a5d)

Change-Id: I7e714b7c4ce34b5285cfbf9ca81133ecbbb16fc1
Reviewed-on: https://gerrit.libreoffice.org/71903
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>