plugin pubsub signature: fix attachment setting + default signer: - attachment setting was crashing when `item_elt` was not specified due to argument typo - if `signer` is set to None in attachment data, client's bare jid will be used to sign the item rel 381

#!/bin/sh

eval $(dbus-launch --sh-syntax)

nohup /usr/bin/Xtigervnc -geometry 1024x768 -desktop "Libervia e2e test" -rfbport 5900 -SecurityTypes None :0 &
nohup openbox &
exec libervia-backend fg