Interactive marker server 'NoneType' object is not callable
I had an error popped out when I click on the interactive menu. However, the menu works somehow. But I still want to eliminate this error.
Traceback (most recent call last): File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/topics.py", line 750, in _invoke_callback cb(msg) File "/opt/ros/melodic/lib/python2.7/dist-packages/interactive_markers/interactive_marker_server.py", line 356, in processFeedback marker_context.default_feedback_cb(feedback) TypeError: 'NoneType' object is not callable