Errors cause a nullpointerexception to occur followed by a crash after trying to generate a world with cleanroomgenerator. The stack trace shows only bukkit classes, though, so I do not know if it can be fixed by editing the code or if this is a bukkit error.

I'd say it's a Bukkit bug, there hasn't been any documented API changes yet, if it's still broken next RB then feel free to re-open the bug report.