Steps to reproduce

1. Have two or three empty tracks
2. Start making a marquee selection starting from the bottom track up and to the left, so that the cursor goes over the track headers
3. (Might need to repeat a few times)
4. Observe

Expected behavior

No crash; the selection propagates over the tracks despite the mouse cursor being in the track headers territory (AU3/AU4 master behavior).

Actual behavior

The selection only touches the bottom-most track, eventually leading to a crash:

Another easy way to reproduce the crash:

Audacity Version

#8876

Operating system

OS independent