Bug#803112: Upgrading kernel fixes bug

I discovered that upgrading to kernel linux-image-4.5.0-2-amd64 fixes this bug completely. To be clear I was on 3.14-rt beforehand and didn't have the correct package installed for the kernel to auto-update to newer versions. However for the benefit of others it's probably worth noting that

Bug#803112: gdm3: Black/grey screen with unresponsive mouse cursor on GDM start

This bug is still present in gdm3 version 3.20.1-1

Bug#803112: Workaround for bug

I found out a proper workaround which is to uncomment the line that says "WaylandEnable=false" in /etc/gdm3/daemon.conf and then reboot. It is necessary to reboot, not just restart gdm3 for some reason. If I just restart gdm3 without rebooting I am presented with a flickering screen instead of