Yeah, I tried this the moment the version was released (using gamestate(84) though). Also, the map isn't just removed -- the entire code for map logic in the normal game seems gone, because you can get a lot of weird gliches beyond just an empty map.
(fun fact: one bug is that if you play a custom level, fire up the continue menu and do a time trial, the game will load the last custom map you played and somehow trying to apply in-game logic to it, breaking it in very interesting and strange ways. And no, merely applying a Dimension VVVVVV map replica will not fix the issues)