Issue in merging PointCloud2 data

[hikashi]

I have the input of multiple pointcloud2 input obtained from the simulated VLP16 sensor in different robots and attempt to combine the point cloud topics from all the robots into one point cloud before feeding it into octomap,
The pointcloud2 stream I used to input is "velodyne_points" and I have the namespace of the turtlebot defined as "tb3_1".

The declaration of the launch file is set up as follows:

    <node pkg="map_merge_3d" type="map_merge_node" respawn="false" name="map_merge_node"  output="screen">
        <param name="robot_map_topic" value="velodyne_points" />
        <param name="robot_namespace" value="tb3" />
        <param name="merged_map_topic" value="merged_map2" />
        <param name="world_frame" value="world" />
        <param name="discovery_rate" value="0.05" />
        <param name="estimation_rate" value="0.01" />
        <param name="compositing_rate" value="0.3"/>
        <param name="publish_tf" value="true"/>
      </node> 

The setup I am using is ROS Melodic with PCL 1.8.1+dfsg1-2ubuntu2.18.04.1
however, I keep getting the following error message:

[pcl::PFHEstimation::compute] input_ is empty!
[pcl::PFHEstimation::initCompute] Init failed.
[pcl::PFHEstimation::compute] input_ is empty!
[pcl::PFHEstimation::initCompute] Init failed.
[pcl::PFHEstimation::compute] input_ is empty!
[pcl::PFHEstimation::initCompute] Init failed.

Let me know if there is a solution or I have done the configuration wrongly.
Thanks.

[Mighteeguy]

@hikashi , did you get the solution?