NiceAgent and it's associated thread is alive for as long as GstWebRTCICE is alive so make sure any signal handlers connected to NiceAgent do not access data that is deleted earlier. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2073>
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1646>