The patched xfce4-session package from the PPA in https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1104435/comments/19 solved it for me.
The patched xfce4-session package from the PPA in https:/ /bugs.launchpad .net/ubuntu/ +source/ xfce4-session/ +bug/1104435/ comments/ 19 solved it for me.