[packagekit] backend initialized multiple times when using pk-application

[Andreas]

Actually it's getting called twice even if you just start
pk-application. pk-application then segfaults in
pk_task_monitor_error_code_cb because alpm fails to lock the db twice.
If I just ignore the error and exit with pk_backend_finished (backend)
(where backend is the PkBackend * parameter passed to my implementation
of backend_initialize) I get

(packagekitd:27562): GLib-GObject-WARNING **: invalid unclassed pointer
in cast to `PkBackend'
[pk_backend_finished_delay] pk-backend.c:791 (21:41:12):         emit
finished 1

(packagekitd:27562): GLib-GObject-WARNING **: instance with invalid
(NULL) class pointer

and the job is still handled as 'in progress'.
backend can't be null as I check with g_return_if_fail at the beginning.
I'll continue research tomorrow.