fix AE Follow craft disconnect the client sometime (#1101)

src/main/java/appeng/client/render/notification/NotificationManager.java

@@ -14,7 +14,7 @@ import cpw.mods.fml.common.gameevent.TickEvent;
  */
 public class NotificationManager {
 
-    public static GuiNotification guiNotification;
+    private static GuiNotification guiNotification;
 
     @SubscribeEvent
     public void renderTick(TickEvent.RenderTickEvent event) {
@@ -25,4 +25,9 @@ public class NotificationManager {
             guiNotification.updateNotificationWindow();
         }
     }
+
+    public static GuiNotification getGuiNotification() {
+        if (guiNotification == null) guiNotification = new GuiNotification(Minecraft.getMinecraft());
+        return guiNotification;
+    }
 }

src/main/java/appeng/core/sync/packets/PacketCraftingCompleteNotification.java

@@ -65,7 +65,7 @@ public class PacketCraftingCompleteNotification extends AppEngPacket {
                 this.stack.getDisplayName(),
                 elapsedTimeText);
 
-        NotificationManager.guiNotification.queueNotification(
+        NotificationManager.getGuiNotification().queueNotification(
                 new Notification(
                         this.stack,
                         StatCollector.translateToLocal("chat.appliedenergistics2.CraftComplete"),