Players can spawn in and take damage or die before the world loads correctly, and then respawn in an incorrect location

Verification builds:
1.10.0.4 Beta
1.9.0

Summary:
Players can spawn into a world and die before the world has finished loading, or before the player has fully joined a multiplayer world. This can result in players dying before they are able to move so safety, and may result in them dying twice and respawning elsewhere.

Steps to Reproduce:

1. Set up a multiplayer game (Player 1 as host, player 2 as guest/client)
2. Fill a large area with stone (/fill ~ ~ ~ ~8 ~8 ~8 stone)
3. Punch a 1x2x3 hole in the stone filled area
4. Reduce Player 2's health to ~2 hearts
5. Have Player 2 enter the hole in the stone, and then exit the world
6. Have Player 1 fill the hole with stone
7. Have Player 2 rejoin the world

Observed Results:
Player 2 rejoins and suffocates in the hole, and dies. They may die again when they fully load in. They will then respawn up on top of the filled stone area.

Expected Results:
Player 2 should not die before they have fully joined the world, and if they do suffocate in the blocks, they should respawn at their set respawn place (bed or world spawn).

Screenshots/Videos attached: No

Notes: