[ROS 2] qt_gui_main() found no plugin matching "rqt_graph.ros_graph.RosGraph"

[fujitatomoya]

I was playing around with ros jazzy and rolling with rqt, and found the following warning.

root@tomoyafujita:~# ros2 run rqt_graph rqt_graph 
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
qt_gui_main() found no plugin matching "rqt_graph.ros_graph.RosGraph"
try passing the option "--force-discover"
Warning: class_loader.ClassLoader: SEVERE WARNING!!! Attempting to unload library while objects created by this loader exist in the heap! You should delete your objects before attempting to unload the library or destroying the ClassLoader. The library will NOT be unloaded.
         at line 127 in ./src/class_loader.cpp
[ros2run]: Process exited with failure 1
root@tomoyafujita:~# ros2 run rqt_graph rqt_graph --force-discover
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
root@tomoyafujita:~# ros2 run rqt_graph rqt_graph 
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'

seems --force-discover works okay, and once it is force loaded, the problem is not reproducible.

I am not sure if this is problem, but as user-experience, it would be nice if that is working out of the box.