Unfortunately I'm still hitting crashes often, when disconnecting a projector from my 2016 Macbook Pro (OSX 10.13.6), this time with Madmapper 3.6.7.
I've noticed the issue when disconnecting either of my two projectors (both Optoma brand, but different models), as well as with a variety of USB-C-to-HDMI dongles.
It doesn't seem to be related to the physical connection, as I notice this even when I simply power off the projector (while leaving the cables inserted). I'm usually running MM in full screen mode when this happens.
I hit 3 crashes in a 1-hour span yesterday. Since MM has no autosave feature, I've lost a decent amount of work from these crashes..