laser_assembler not gathering clouds

edit

I've been trying to use laser_assembler package to gather every single cloud that is publish by another node. For this, I've created a client node to define the service needed from the laser_assembler package(included in launch file). However, I still couldn't be able to have the clouds gathered.

The client code:

    void AssemblerClient::useAssembler(const sensor_msgs::LaserScanConstPtr& scan_ptr)
    {
      ROS_INFO("Assembler service is being used");
      ros::service::waitForService("assemble_scans");
      ros::ServiceClient client = n.serviceClient<AssembleScans>("assemble_scans");
      AssembleScans srv;
      srv.request.begin = ros::Time(0);
      srv.request.end   = ros::Time::now();
      if (client.call(srv))
        ROS_INFO("Got cloud with %u points\n", srv.response.cloud.points.size());
      else
        ROS_INFO("Service call failed\n");
    }

In the launch file:

<node type="point_cloud_assembler" pkg="laser_assembler" name="my_assembler">
  <remap from="cloud" to="cloud"/>
  <param name="max_clouds" type="int" value="4000" />
  <param name="fixed_frame" type="string" value="world" />
</node>

<node pkg="pcd_bot" type="assembler_client_node" name="assembler_client_node">
</node>

Am I missing something?

Thanks in advance.

EDIT

No error at all I receive but in the rviz, I even cannot choose/tick for "assemble_scans" topic of type PointCloud.

I've added the following 2 lines at the bottom of the above code snippet(but still doesn't work):

gathered_cloud = srv.response.cloud;
gathered_cloud_publisher_.publish(gathered_cloud);