Should fix coverity CID 1401760.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190605145829.7674-2-marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>