Just shows low-res blank screen if remote machine's refresh > 60 Hz

If the remote machine's refresh rate is > 60 Hz (or at least when it's slightly above), VNC clients just show a low-res (800x600) near-black blank screen when connected to gnome-remote-desktop. Input events work as normal (modulo other input bugs recently reported).

Remote machine 1 @ 60.0005 Hz: fails

Remote machine 1 @ 59.9407 Hz: works

Remote machine 2 @ 59.9979 Hz: works

Remote machine 3 @ 59.9872 Hz: works

Remote machine 4 @ 59.9553 Hz: works