...cycles involving a mix of formula-groups and plain
formula-cells which are not grouped.

This fixes a crash in tdf#104213/1

Change-Id: I63b8b7379e4e5eaf322a3318f061a9e5fbc931ef
Reviewed-on: https://gerrit.libreoffice.org/57031
Tested-by: Jenkins
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>