Tje following steps results in a crash for me. It doesn't ask for a crash report, just closes xLights. I can't use a previous view to make a new master view.
I was able to repeat it 3 consecutive times. Once after a full reboot of the PC. This is on Windows, I haven't tried my Mac version yet.
Create New Sequence - Musical
Edit Display Elements
Select View (any previous view)
Make Master