error: Remove NULL checks on error_propagate() calls

Patch created mechanically by rerunning:

  $  spatch --sp-file scripts/coccinelle/error_propagate_null.cocci \
            --macro-file scripts/cocci-macro-file.h \
            --dir . --in-place
Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Message-Id: <20180705155811.20366-3-f4bug@amsat.org>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

hw/s390x/virtio-ccw.c

@@ -1836,11 +1836,9 @@ static void vhost_vsock_ccw_realize(VirtioCcwDevice *ccw_dev, Error **errp)
 {
     VHostVSockCCWState *dev = VHOST_VSOCK_CCW(ccw_dev);
     DeviceState *vdev = DEVICE(&dev->vdev);
-    Error *err = NULL;
 
     qdev_set_parent_bus(vdev, BUS(&ccw_dev->bus));
-    object_property_set_bool(OBJECT(vdev), true, "realized", &err);
-    error_propagate(errp, err);
+    object_property_set_bool(OBJECT(vdev), true, "realized", errp);
 }
 
 static void vhost_vsock_ccw_class_init(ObjectClass *klass, void *data)