Fix memory leak

src/main/java/com/songoda/ultimatestacker/UltimateStacker.java

@@ -116,6 +116,7 @@ public class UltimateStacker extends SongodaPlugin {
     @Override
     public void onPluginEnable() {
         // Run Songoda Updater
+        Async.start();
         SongodaCore.registerPlugin(this, 16, CompatibleMaterial.IRON_INGOT);
         // Setup Config
         Settings.setupConfig();

src/main/java/com/songoda/ultimatestacker/stackable/entity/EntityStack.java

@@ -130,9 +130,9 @@ public class EntityStack extends ColdEntityStack {
         }
 
         event.getDrops().clear();
+        plugin.getEntityStackManager().removeStack(event.getEntity());
         if (killed.getKiller() == null) return;
         plugin.addExp(killed.getKiller(), this);
-        plugin.getEntityStackManager().removeStack(event.getEntity());
     }
 
     private void handleSingleStackDeath(LivingEntity killed, List<Drop> drops, int droppedExp, EntityDeathEvent event) {

src/main/java/com/songoda/ultimatestacker/utils/Async.java

@@ -5,7 +5,11 @@ import java.util.concurrent.Executors;
 
 public class Async {
 
-    private static ExecutorService executor = Executors.newFixedThreadPool(10);
+    private static ExecutorService executor;
+
+    public static void start() {
+        executor = Executors.newFixedThreadPool(5);
+    }
 
     public static void run(Runnable runnable) {
         executor.execute(runnable);