[#910] control: Take empty namespace for 'root'

Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>

pkg/services/control/server/policy_engine.go

@@ -17,7 +17,12 @@ func apeTarget(chainTarget *control.ChainTarget) (engine.Target, error) {
 	case control.ChainTarget_CONTAINER:
 		return engine.ContainerTarget(chainTarget.GetName()), nil
 	case control.ChainTarget_NAMESPACE:
-		return engine.NamespaceTarget(chainTarget.GetName()), nil
+		namespace := chainTarget.GetName()
+		// If namespace is empty, we take it for root namespace.
+		if namespace == "" {
+			namespace = "root"
+		}
+		return engine.NamespaceTarget(namespace), nil
 	default:
 	}
 	return engine.Target{}, status.Error(codes.InvalidArgument,