Null pointer exception in physics server deleting floor bodies with new move and slide logic

[omegachysis]

Godot version

3.4.stable

System information

Pop!_OS 21.04, NVIDIA Corporation GK104 [GeForce GTX 770], GLES3

Issue description

Using the new move_and_slide_with_snap logic results in null pointer exceptions when a floor body is freed while a kinematic body is colliding with it.

ERROR: Condition "!body" is true. Returned: nullptr
   at: body_get_direct_state (modules/bullet/bullet_physics_server.cpp:855)
ERROR: Condition "!id_map.has(p_rid.get_data())" is true. Returned: nullptr
   at: get (./core/rid.h:140)

I believe this is because of the check here:

godot/scene/3d/physics_body.cpp

Lines 1070 to 1072 in 489b49c

	if (on_floor && on_floor_body.is_valid()) {
	// This approach makes sure there is less delay between the actual body velocity and the one we saved.
	PhysicsDirectBodyState *bs = PhysicsServer::get_singleton()->body_get_direct_state(on_floor_body);

If the object on_floor_body points to is freed, the RID doesn't exist (but remains 'valid' in the kinematic body).

Steps to reproduce

1. Create static body and a kinematic body.
2. Make kinematic body collide with static body and sit on it as a floor.
3. Call move_and_slide every physics tick and free the static body.

Minimal reproduction project

platform-deletion.zip

[arkology]

I'm almost sure this is definitely a duplicate of already existing issue and has already been fixed.
Upd: Duplicate of #54666

[omegachysis]

#54666 I see it now, I must have filtered by open issues by accident. Closing.