Number checker aborts after completion

[threent2]

After resolving a few inconsistencies of PublishResult vs PublishedResult between the code and xml (I standardised on PublishResult) the program runs and appears to run to SUCCESS but then aborts.

Screen output

brian@HP-laptop:~/master_ros2_ws$ ros2 launch first_bts number_checker.launch.py
[INFO] [launch]: All log files can be found below /home/brian/.ros/log/2025-09-27-14-42-07-478976-HP-laptop-19181
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [number_checker-1]: process started with pid [19184]
[number_checker-1] [INFO] [1758980528.061331937] [rclcpp]: QUI!.
[number_checker-1] Generated number: 79 - Threshold: 30 - Failure!
[number_checker-1] Generated number: 9 - Threshold: 50 - Success!
[number_checker-1] terminate called after throwing an instance of 'rclcpp::exceptions::InvalidTopicNameError'
[number_checker-1] what(): Invalid topic name: topic name must not be empty string:
[number_checker-1] ''
[number_checker-1] ^
[number_checker-1]
[ERROR] [number_checker-1]: process has died [pid 19184, exit code -6, cmd '/home/brian/master_ros2_ws/install/lib/first_bts/number_checker --ros-args -r __node:=number_checker --params-file /tmp/launch_params_f4xnhmgz'].

I tried looking at the error using gdb but my C++ knowledge is not up to the task.