003387fab5
rB568f0c7 added a recursion check that is supposed to prevent cyclic cases where a group includes itself via dupli instancing. The check function was descending into all groups nested inside the target group - which works for single level recursion like in the test case, but does not handle generic recursion. Basically it asked: "is object X in the group already or in any instanced dupligroup?" The new check instead asks: "is group G dupli'd by X or any instanced subgroup thereof?" which is what we really need to know.