stats: vpp_get_stats crashes in stat_segment_data_free

STAT_DIR_TYPE_EMPTY is not handled. This can happen when the
interface is deleted.

Type: fix

Signed-off-by: Steven Luong <sluong@cisco.com>
Change-Id: Ic1f5a1a0e7005059628d1dde31118d692c1967d8
diff --git a/src/vpp-api/client/stat_client.c b/src/vpp-api/client/stat_client.c
index 2c30be6..b0c8391 100644
--- a/src/vpp-api/client/stat_client.c
+++ b/src/vpp-api/client/stat_client.c
@@ -338,6 +338,7 @@
 	  vec_free (res[i].error_vector);
 	  break;
 	case STAT_DIR_TYPE_SCALAR_INDEX:
+	case STAT_DIR_TYPE_EMPTY:
 	  break;
 	default:
 	  assert (0);