(#3220) fix an edge case wrt. the generating of additional graph edges

The fix for #22229 saw fit to add a graph edge for each generated resource,
originating from the container of whichever resource was responsible for
the generating in the first place.

In any regular catalog, this will work without issue. During integration
testing of the cron provider, however, artificial catalogs are used in which
there is not even a Main class to contain all globally scoped resources.
As a result, the test would not run because of the dangling edge.

To keep this from happening, add a sanity check to the code that is
responsible for creating the additional edges.