dev could be NULL if the PCI device can not be found due to some
reasons, so we must not dereference the pointer in this case.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 1519713884-2346-1-git-send-email-thuth@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>