This error always existed as qdev_init() frees the object. But QOM
goes a bit further and purposefully sets the class pointer to NULL to
help find use-after-free. It worked :-)
Cc: Andreas Faerber <afaerber@suse.de> Reported-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>