refactor(service/share): GetSharesByNamespace - no error if namespace…

… not found

* This is simillar to changes introduced in #661 in IPLD package.
* Test was broken - `Error` checks for error and prints a message
  (there's `ErrorContains` for string comparison)

service/share/share.go

@@ -159,7 +159,7 @@ func (s *service) GetSharesByNamespace(ctx context.Context, root *Root, nID name
 		}
 	}
 	if len(rowRootCIDs) == 0 {
-		return nil, format.ErrNotFound
+		return nil, nil
 	}
 
 	errGroup, ctx := errgroup.WithContext(ctx)

service/share/share_test.go

@@ -108,13 +108,13 @@ func TestGetShares(t *testing.T) {
 	require.NoError(t, err)
 }
 
-func TestService_GetSharesByNamespaceNotFoundInRange(t *testing.T) {
+func TestService_GetSharesByNamespaceNotFound(t *testing.T) {
 	serv, root := RandLightServiceWithSquare(t, 1)
 	root.RowsRoots = nil
 
 	shares, err := serv.GetSharesByNamespace(context.Background(), root, []byte(""))
 	assert.Len(t, shares, 0)
-	require.Error(t, err, "namespaceID not found in range")
+	assert.NoError(t, err)
 }
 
 func BenchmarkService_GetSharesByNamespace(b *testing.B) {