Comment 28 for bug 1303736

I can note that I also suffer from the issue when I disable suspending when closing the laptop lid: Settings > Power Manager > When laptop screen is closed: "Lock Screen". In this case light-locker still locks the screen when closing the lit and the laptop display itself is also shutdown. When suspending, the laptop screen also is shutdown.

So rather than 'suspend to RAM' being the culprit I argue that powering off the laptop screen (which happens both with and without suspend when closing the lid) is the cause for the blank screen after unlocking. I can confirm that the xrandr fix also works in this case (which lead me to suspect it has to do something with the monitor being shutdown), unfortunately "Configure new displays when connected" under Settings > Displays doesn't seem to do the trick.