As title says, using F3+N to go back to creative when joining a world as spectator doesn't work.

Steps to reproduce:

1. Join a singleplayer world and go into spectator mode
2. Save and quit to title
3. Join the world again
4. Press F3+N to switch gamemode; nothing happens

F3+N will only work again after manually going into creative again (via /gamemode creative)

Additional info

• F3+F4 works as expected.
• The issue doesn't occur on servers. 
• Restarting the game before joining again doesn't help.
• I haven't tested on other versions yet.