Repair broken xfce after theme selection

I have an Ubuntu upgraded to Kubuntu now upgraded to Xubuntu (seems the best). Playing around with theme selection, sometimes crashes xfce with no chances of getting back in.

I had other  WMs so I just entered Gnome and run /usr/bin/xfce-setting-show to change the theme back.

I don’t have a solution if xfce is your only session type, but I suspect this problem would not arise either.