I've just tried a simpler version with just midi track (no soft synth requires) :
- start with a blank project
- insert a midi track, record a simple midi clip
- drag midi clip down to empty area, thus, creating a new midi track
* at this moment, track 2 is in blue color (mark selected, due to our last action of dragging the clip down).
- move mouse to track 1, right click and select delete track (the delete track option did not specify now many tracks)
- deleting track 1, now caused track 2 to be deleted as well.