trivial: Show a warning if the child device gets unref'd from the parent
trivial: Show a warning if the child device gets unref'd from the parent

Should not happen, but bugs will be bugs.

fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd,hughsie/fwupd