Bug - Selecting new bag file when an existing bag file is still playing does not stop existing bag file
Summary
When playing back a bag file with the playback GUI, failing to Pause or Stop a bag file before selecting and playing a new bag file will result in both bag files playing at the same time. Furthermore, it is not possible to stop the first bag file without shutting down the playback GUI and relaunching the program
Steps to reproduce
Select a bag file from the playback GUI and click 'Play'. Once the bag file is being played back, choose 'Select file' again and open another bag file. Click 'Play' and observe both files being played back at the same time (note the constant flickering between messages of the numerous bag files)
Possible fixes
Call the method invoked by the 'Stop' (or 'Pause') button when the 'Select file' button is clicked