Guard mbedtls_ssl_get_peer_cert() by new compile-time option
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 141c255..df5e036 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -8666,7 +8666,11 @@
     if( ssl == NULL || ssl->session == NULL )
         return( NULL );
 
+#if defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
     return( ssl->session->peer_cert );
+#else
+    return( NULL );
+#endif /* MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
 }
 #endif /* MBEDTLS_X509_CRT_PARSE_C */