Some shapes do not contain polyline and meanwhile contain start/end
arrows. This is causing unexpected line endings appear in export.

TODO: Unittest is disabled, since XML parsing returns only root node
without children. So XPATH assert fails.

Change-Id: Ibc28f12b0f3838065978a674f0debe8e1b8103e9
Reviewed-on: https://gerrit.libreoffice.org/40422Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>