Session/tcp coverity fixes

Change-Id: Ic5467df16e870b49c49678b1dbb40f4a2390b3c9
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/tcp/builtin_client.c b/src/vnet/tcp/builtin_client.c
index 276beb2..32d69a9 100644
--- a/src/vnet/tcp/builtin_client.c
+++ b/src/vnet/tcp/builtin_client.c
@@ -56,6 +56,9 @@
   session_fifo_event_t evt;
   static int serial_number = 0;
   int rv;
+
+  ASSERT (vec_len (test_data) > 0);
+
   test_buf_offset = s->bytes_sent % vec_len (test_data);
   bytes_this_chunk = vec_len (test_data) - test_buf_offset;