Description:
When loading a singleplayer world the load function from a datapacks is executed without the player.

How to reproduce:
1. create a world
2. leave world
3. add datapack that tests if a player exists on load (example in attachments)
4. join world
5. look into the logs

Expected:
The datapack finds the player

Reality:
The datapack doesn't find the player

Additional note:
The first ticks are also executed before the player is in the world