I perform following operations:
$ roslaunch utbm_dataset_play.launch bag:=utbm_robocar_dataset_20180719_noimage.bag
$ rostopic echo /nmea_sentence
WARNING: no messages received and simulated time is active.
Is /clock being published?
$ rqt_graph

It seems like that the topic '/nmea_sentence' is not processed by the node '/nmea_topic_driver'. Why it happens?