avoid relaying changes if theres no one listening to the passthrough

src/api/java/appeng/api/storage/IMEMonitorHandlerReceiver.java

@@ -52,4 +52,9 @@ public interface IMEMonitorHandlerReceiver<T extends IAEStack<T>>
 	 * called when the list updates its contents, this is mostly for handling power events.
 	 */
 	void onListUpdate();
+
+	default boolean hasListeners()
+	{
+		return true;
+	}
 }

src/main/java/appeng/me/cache/NetworkMonitor.java

@@ -262,7 +262,7 @@ private void notifyListenersOfChange( final Iterable<T> diff, final IActionSourc
 		{
 			final Entry<IMEMonitorHandlerReceiver<T>, Object> o = i.next();
 			final IMEMonitorHandlerReceiver<T> receiver = o.getKey();
-			if( receiver.isValid( o.getValue() ) )
+			if( receiver.isValid( o.getValue() ) && receiver.hasListeners() )
 			{
 				receiver.postChange( this, diff, src );
 			}

src/main/java/appeng/me/storage/MEMonitorPassThrough.java

@@ -90,6 +90,13 @@ public IItemList<T> getAvailableItems( final IItemList out )
 	@Override
 	public void addListener( final IMEMonitorHandlerReceiver<T> l, final Object verificationToken )
 	{
+		if( this.listeners.size() == 0 )
+		{
+			if( this.monitor != null )
+			{
+				this.monitor.addListener( this, this.monitor );
+			}
+		}
 		this.listeners.put( l, verificationToken );
 	}
 
@@ -117,6 +124,12 @@ public boolean isValid( final Object verificationToken )
 		return verificationToken == this.monitor;
 	}
 
+	@Override
+	public boolean hasListeners()
+	{
+		return this.listeners.size() > 0;
+	}
+
 	@Override
 	public void postChange( final IBaseMonitor<T> monitor, final Iterable<T> change, final IActionSource source )
 	{