I did an update on Mint and the screen going blank and presenting with a lock
screen as it should went away. Well, after nearly posting on the official
forum, I finally figured out what to do. The upgrade migrated to
xfce4-screensaver. However, the upgrade did not install xfce4-screensaver!
What I did was make sure xfce4-screensaver was actually installed then go
into "Session and Startup" and make sure "Light Locker" and the correct
"Screensaver" (and no other "Screensaver"s) were selected and after a reboot I
was good to go.