Blank VPN tab when creating or editing connection in nm-connection-editor

Description:

When creating a new vpnc connection or editing an existing one in nm-connection-editor the VPN tab is blank. This happens after upgrading networkmanager-vpnc from 1.2.8-3 to 1.4.0-1. The connection itself for existing configuration works without any problems.

Additional info:

• package version(s): ** networkmanager 1.50.0-1 ** networkmanager-vpnc 1.4.0-1 ** nm-connection-editor 1.36.0-1
• config and/or log files: Nothing is logged
• link to upstream bug report: https://gitlab.gnome.org/GNOME/NetworkManager-vpnc/-/issues/14

Steps to reproduce:

1. run nm-connection-editor
2. click "+" button to add a new connection
3. in the new window select "Cisco Compatible VPN (vpnc)" as Connection Type
4. click "Create..."
5. you'll see the blank VPN tab in the Edit VPN connection window

Workaround:

Downgrading networkmanager-vpnc to 1.2.8-3 fixes the problem.