fix miss sent extensions mask

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index c6fa3b3..90f54f9 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -1022,6 +1022,8 @@
 
     MBEDTLS_SSL_DEBUG_BUF(3, "pre_shared_key identities", buf, p - buf);
 
+    mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_PRE_SHARED_KEY);
+
     return 0;
 }