Starting a recording while one is already running

Several issues with this:

1. If you are recording and you hit record again it allows it, it seems, and it shouldn't.
2. It also causes the file to not zip correctly via long press. My Samsung S20 cannot unzip the .zip it creates, but my Windows 10 PC can with 7zip.
3. It won't record the end time correctly in the "View saved data" section.
4. The "invoke file conversion" button produces an error ("error during conversion")

The fix would probably be to produce an error message "Recording already in process" and do nothing else when that button is pressed.