Fix lap cheat prevention failing when player dies

- Cross a finish line so your lap goes forward and your
  waypoints update ahead of the line
- Turn around to face the opposite direction
- Do this on a map where the lap cheat timer activates
  when you turn around
- Drive a little way backward and make sure the lap cheat
  timer keeps going
- Activate Ring Shooter and start lightsnaking
- Immediately spectate and then rejoin
- The lightsnake would send you ahead of the finish line
  and give you an extra lap

src/g_game.c

@@ -2209,6 +2209,31 @@ void G_PlayerReborn(INT32 player, boolean betweenmaps)
 	// SRB2kart
 	memcpy(&itemRoulette, &players[player].itemRoulette, sizeof (itemRoulette));
 	memcpy(&respawn, &players[player].respawn, sizeof (respawn));
+
+	// Here's the exact scenario:
+	// - Respawn with Ring Shooter (or lightsnake in general)
+	// - Spectate, re-enter the game
+	// - Now respawn.pointxyz is set to where the player
+	//   spectated
+	// - K_DoIngameRespawn will be called after
+	//   G_PlayerReborn (in P_MovePlayerToCheatcheck)
+	// - If the respawn state is not reset here, then the
+	//   call to K_DoIngameRespawn will do nothing, and
+	//   respawn.pointxyz will stay the same
+	// - This is bad, because when K_RespawnChecker runs, it
+	//   clears the init state once the player reaches
+	//   respawn.pointxyz
+	// - This is because it assumes respawn.pointxyz is where
+	//   the respawn waypoint is located
+	// - In other words, the init state will reset before
+	//   lightsnake reaches the respawn waypoint
+	// - This is bad because lap cheat prevention relies on
+	//   the init state being cleared after reaching the
+	//   respawn waypoint (because moving to the respawn
+	//   waypoint could cross a finish line the wrong way and
+	//   lose a lap)
+	respawn.state = RESPAWNST_NONE;
+
 	memcpy(&public_key, &players[player].public_key, sizeof(public_key));
 
 	if (betweenmaps || leveltime < introtime)