time_since_death increments even when player doesn't exist

When loading/joining into a world, the `time_since_death` custom stat increments, even when the player isn't actively "alive." This makes getting events to happen as soon as they spawn in with joining/loading inaccurate and harder to perfect.

Attached are the three images of the world loading and then joining the world, and lastly showing the `time since death` timer already being at 100, even though the player was "just" created. This is known because `@a` and `@s` selectors do not find the player and cannot change anything about the player until the player has fully joined the world.