wwan: Don't access free'd error

The error in wwan_manager_password_sent_cb is g_autoptr so we need to steal it when propagating it upwards.

We also need to copy it when add it to an object that outlives the function via g_object_set_data.

Fixes: 00a872ca ("Re-write wwan plugin") Signed-off-by: Guido Günther agx@sigxcpu.org