The basefield flag of a stream is persistent, which I didn't realise before.
This fixes commit 256e42646b
Change-Id: Ic0076c63ae6236ae75dcd79d108add27391b2125
Reviewed-on: https://gerrit.libreoffice.org/3842
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>