Ported 1.17.1-2.1.1 to 1.18.1.

src/main/java/dev/micle/loginprotection/events/OnPlayerLeaveEventHandler.java

@@ -0,0 +1,16 @@
+package dev.micle.loginprotection.events;
+
+import dev.micle.loginprotection.LoginProtection;
+import net.minecraft.world.entity.player.Player;
+import net.minecraftforge.event.entity.player.PlayerEvent;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+
+public class OnPlayerLeaveEventHandler {
+    @SubscribeEvent
+    public void PlayerLeaveEvent(PlayerEvent.PlayerLoggedOutEvent event) {
+        if (!(event.getEntity() instanceof Player)) { return; }
+        Player player = event.getPlayer();
+
+        LoginProtection.protected_players.removePlayer(player.getUUID());
+    }
+}