remove players from npc viewer lists on player disconnect

plugin/src/main/java/lol/pyr/znpcsplus/ZNpcsPlus.java

@@ -41,6 +41,7 @@ import lol.pyr.znpcsplus.scheduling.TaskScheduler;
 import lol.pyr.znpcsplus.skin.cache.MojangSkinCache;
 import lol.pyr.znpcsplus.skin.cache.SkinCacheCleanTask;
 import lol.pyr.znpcsplus.tasks.HologramRefreshTask;
+import lol.pyr.znpcsplus.tasks.NpcHideListener;
 import lol.pyr.znpcsplus.tasks.NpcProcessorTask;
 import lol.pyr.znpcsplus.updater.UpdateChecker;
 import lol.pyr.znpcsplus.updater.UpdateNotificationListener;
@@ -167,6 +168,7 @@ public class ZNpcsPlus extends JavaPlugin {
         scheduler.runDelayedTimerAsync(new NpcProcessorTask(npcRegistry, configManager, propertyRegistry), 60L, 3L);
         scheduler.runDelayedTimerAsync(new HologramRefreshTask(npcRegistry), 60L, 20L);
         scheduler.runDelayedTimerAsync(new SkinCacheCleanTask(skinCache), 1200, 1200);
+        pluginManager.registerEvents(new NpcHideListener(npcRegistry), this);
 
         log(ChatColor.WHITE + " * Loading data...");
         npcRegistry.reload();

plugin/src/main/java/lol/pyr/znpcsplus/tasks/NpcHideListener.java

@@ -0,0 +1,21 @@
+package lol.pyr.znpcsplus.tasks;
+
+import lol.pyr.znpcsplus.npc.NpcRegistryImpl;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerQuitEvent;
+
+public class NpcHideListener implements Listener {
+    private final NpcRegistryImpl registry;
+
+    public NpcHideListener(NpcRegistryImpl registry) {
+        this.registry = registry;
+    }
+
+    @EventHandler
+    public void onQuit(PlayerQuitEvent event) {
+        registry.getProcessable().forEach(entry -> {
+            if (entry.getNpc().isVisibleTo(event.getPlayer())) entry.getNpc().UNSAFE_removeViewer(event.getPlayer());
+        });
+    }
+}

plugin/src/main/java/lol/pyr/znpcsplus/util/Viewable.java

@@ -37,6 +37,10 @@ public abstract class Viewable {
         UNSAFE_hide(player);
     }
 
+    public void UNSAFE_removeViewer(Player player) {
+        viewers.remove(player);
+    }
+
     protected void UNSAFE_hideAll() {
         for (Player viewer : viewers) UNSAFE_hide(viewer);
     }