Switching to Spectator mode puts the player in a weird state until they cross a chunk border when spectatorsGenerateChunks is false

When switching to spectator mode, it takes a bit to register that you are actually in spectator mode rather than instantly. You have to cross a chunk border to fully register the gamemode change.

Steps to Reproduce:

1. Equip an elytra

2. Set the gamerule spectatorsGenerateChunks to false

3. Make sure you are in the middle of a chunk (including vertical chunk)

4. Enter fly mode then use the f3+n hotkey to switch to spectator mode

5. ❌ You enter a weird mode until you cross a chunk border