Bad state: No element error in VlcStatusResponse.state when a password hasn't been set for VLC's HTTP interface

[insin]

When a password isn't set, VLC returns this for /requests/status.xml:

Password for Web interface has not been set.

Please use --http-password, or set a password in

Preferences > All > Main interfaces > Lua > Lua HTTP > Password.

This message is localised, so if the response isn't valid XML and contains --http-password we can prompt the user to enter a password and restart VLC, with a link to the guide docs if they need it.