Don't cache empty session ID nor resumed session
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index faa110a..5b421fc 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -1303,6 +1303,7 @@
      */
     if( ssl->handshake->resume == 0 &&
         ssl->renegotiation == SSL_INITIAL_HANDSHAKE &&
+        ssl->session_negotiate->length != 0 &&
         ssl->f_get_cache != NULL &&
         ssl->f_get_cache( ssl->p_get_cache, ssl->session_negotiate ) == 0 )
     {