The bug
When quitting the world right before the beams appear from the End Crystals when respawning the Ender Dragon with the naturally generated portal in the End causes Minecraft to stop respond and freeze.
Related issues
Comments


Either local name server problem or Mojang's auth server (temporarily) down:
[14:56:22] [pool-2-thread-1/WARN]: Couldn't look up profile properties for com.mojang.authlib.GameProfile@2c4c0e56[id=9a6ad051-c3d8-43c6-b1d9-670045e01bd0,name=Swekob,properties={},legacy=false]
com.mojang.authlib.exceptions.AuthenticationUnavailableException: Cannot contact authentication server
Caused by: java.net.UnknownHostException: sessionserver.mojang.com

Should I be connected to the internet to make the log valid?
And by the way, can someone else confirm this? Attach your log if confirmed.

Yes, please redo this while online.

Might be caused by MC-92255

Please check if that's still an issue in the latest snapshot.

Can no longer reproduce (1.14.4)
After having this issue: Please attach the complete output of the "Game Output (Your Minecraft name) " which can be found on the fourth tab of the launcher to this ticket.
If the launcher closes after game start, please edit your profile and select "Launcher visibility" then, "Keep the launcher open".