Handle empty root in config

If the config.toml has an empty root specified, this could be
passed to the NVIDIA Container CLI through the --root flag
which causes argument parsing to fail. This change only
adds the --root flag if the config option is specified
and is non-empty.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

cmd/nvidia-container-runtime-hook/main.go

@@ -92,7 +92,7 @@ func doPrestart() {
 	rootfs := getRootfsPath(container)
 
 	args := []string{getCLIPath(cli)}
-	if cli.Root != nil {
+	if cli.Root != nil && *cli.Root != "" {
 		args = append(args, fmt.Sprintf("--root=%s", *cli.Root))
 	}
 	if cli.LoadKmods {