The base UnoControl uses WeakAggImplHelper9, so (for better or worse) derives
from XAggregation, but SbaXGridControl failed to properly implement the
XAggregation protocol.
Change-Id: I26c825b9b64b4e886e69f95bc3d4d5d42120bd8a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/145865
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
