I checked both .world files and saw issue in The_RC_Car_World.world
I found that, in the The_RC_Car_World.world file, the model names contains some special character which is not understood by API.
One of place of special character I am showing below.
Avoid above 'ß' character in .world file. This is not readable by API.
Further, when I removed this character, updated my .world file and run Simulink model then I am able to see topics as,
So, remove the above mentioned character, each and every place from .world file. You will able to get topics.
Let me know, if stil you find any issue.