Prevent despawned navigators being readded (#7574)

patches/server/Optimise-WorldServer-notify.patch

@@ -117,7 +117,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
      public void tickNonPassenger(Entity entity) {
          // Paper start - log detailed entity tick information
          io.papermc.paper.util.TickThread.ensureTickThread("Cannot tick an entity off-main");
-+        this.entityManager.updateNavigatorsInRegion(entity); // Paper - optimise notify
++        if (!entity.isRemoved()) this.entityManager.updateNavigatorsInRegion(entity); // Paper - optimise notify
          try {
              if (currentlyTickingEntity.get() == null) {
                  currentlyTickingEntity.lazySet(entity);