Using the latest version 3.0.4 (3100).
I realize that this is not appropriate for font building, but when adding a component that contains a circular reference (component contains a composite glyph that contains that component), Glyphs app crashes. So I have never seen a “bad reference” placeholder.
The circular reference itself is not correct, but I don’t think the app crashing is the correct behavior either.
It would be nice if you could fix this in your spare time.