When plugin_loader_load_and_sync returns false in plugin_loader_replay_pending,
the cur Glist l->pending_plugins will be added to the blacklist.
However, the l->pending_plugins might have already been loaded and freed in handle_rx_packet,
so causing a use-after-free issue.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8747>