x11vnc -solid or -xrefresh options cause unity-greeter to segfault in gdk_window_get_type_hint()

Running x11vnc with either the -solid or -xrefresh options causes unity-greeter to segfault once the VNC client connects.

To reproduce (assuming two machines named 'local-machine' and 'remote-machine'):

  1. ensure that nobody is logged in to 'remote-machine' (unity-greeter should be displayed)
  2. on 'local-machine' run:

        ssh -L 5900:localhost:5900 remote-machine 'sudo \
            x11vnc -localhost -auth /var/lib/lightdm/.Xauthority \
            -display :0 -rfbport 5900 -nopw -solid black'

     or:

        ssh -L 5900:localhost:5900 remote-machine 'sudo \
            x11vnc -localhost -auth /var/lib/lightdm/.Xauthority \
            -display :0 -rfbport 5900 -nopw -xrefresh 5.0'

  3. on 'local-machine', use a VNC client to connect to localhost:5900

unity-greeter on 'remote-machine' will then crash (causing lightdm to respawn it), and the x11vnc program will print "caught XIO error" and exit with a non-zero return code.

Neither of these options cause any problems when connecting via VNC when a user is already logged in.

Additional details:

$ lsb_release -rdc
Description: Ubuntu 12.10
Release: 12.10
Codename: quantal

unity-greeter version: 12.10.4-0ubuntu5
x11vnc version: 0.9.13-1ubuntu1
libvncserver0 version: 0.9.9+dfsg-1
lightdm version: 1.4.0-0ubuntu2