before that there were imported two GroupShapes:
	- empty one with properties like id, name, InteropGrapBag
	- second one with actual shapes

also fixed tests that relyed on that behaviour

Change-Id: I2b94a53e21666b16725c4353448d75e916e4f9df
Reviewed-on: https://gerrit.libreoffice.org/69252
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Reviewed-on: https://gerrit.libreoffice.org/72472