Thank you for taking the time to report this bug.
Do you use a standard Gnome desktop in Ubuntu?
This is certainly a bug in Kupfer's "Common" plugin that currently handles session management (and should be rewritten).
Do any of these two commands give the desired dialog?
gnome-panel-logout --shutdown gnome-session-save --shutdown-dialog
Thank you for taking the time to report this bug.
Do you use a standard Gnome desktop in Ubuntu?
This is certainly a bug in Kupfer's "Common" plugin that currently handles session management (and should be rewritten).
Do any of these two commands give the desired dialog?
gnome-panel-logout --shutdown
gnome-session-save --shutdown-dialog