fix review comments

Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
diff --git a/include/mbedtls/debug.h b/include/mbedtls/debug.h
index 3ca8840..7f813a3 100644
--- a/include/mbedtls/debug.h
+++ b/include/mbedtls/debug.h
@@ -82,7 +82,9 @@
 #define MBEDTLS_SSL_DEBUG_ECP(level, text, X)         do { } while (0)
 #define MBEDTLS_SSL_DEBUG_CRT(level, text, crt)       do { } while (0)
 #define MBEDTLS_SSL_DEBUG_ECDH(level, ecdh, attr)     do { } while (0)
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3) && defined(MBEDTLS_SSL_SESSION_TICKETS)
 #define MBEDTLS_SSL_DEBUG_TICKET_FLAGS(level, flag)   do { } while (0)
+#endif
 
 #endif /* MBEDTLS_DEBUG_C */
 
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 9b34e4f..db2e758 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -96,7 +96,7 @@
 /* Error space gap */
 /** Processing of the Certificate handshake message failed. */
 #define MBEDTLS_ERR_SSL_BAD_CERTIFICATE                   -0x7A00
-/** The kex mode allowed by ticket is not supported by client */
+/** No suitable key exchange mode for ticket */
 #define MBEDTLS_ERR_SSL_TICKET_INVALID_KEX_MODE           -0x7A80
 /**
  * Received NewSessionTicket Post Handshake Message.