Just want to report that I am also getting pointed to a null constellation at the end of the Halbmond research chain in the latest update. According to my save, it's suppose to be in the Siren Constellation. It's been a long time since I've played without mods or Nex, so I have no clue if that's being added in by a mod or not, and a quick search did not return any results. But unlike user Aevita, who's post helped me check my save file, the Siren constellation in my save does not have "null" as a secondary name.
Oh, maybe this might be the cause? The specific system in the Siren constellation that the Traumtanzer was located in had a planet colonized by the Persean League. I'm not 100% sure when they colonized it, if it was before or after the research finished for the Halbmond, but maybe that might be what's causing issues?