The intention for the parallel import is that the number of input and
output arguments is always the same. On error just empty references are
returned.

That means we should not check for empty references here, otherwise the
input and output length won't equal.

Change-Id: Ief86162e7f827bc413c4dde4a4c9f606a83ea803
Reviewed-on: https://gerrit.libreoffice.org/38316Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>