Gamemode isn't correct in Debug Mode

The Bug

In 21w03a, when going through them, nether portals crash the game and the game mode is reported as whatever it was set to before changing it to Debug Mode.

How to Reproduce

1. Create a new world and set the gamemode to something. Now set it to Debug Mode.

2. Press Done and the Game Mode is still reported as the gamemode you chose before.

3. In the world itself:

4. Go through the nether portal at 63 70 83 in creative/survival mode. (Yes, I know debug mode is only supposed to be used in spectator.)

5. The game loads, then crashes.