Adapt mbedtls_ssl_session_copy() to removal of `peer_cert` field
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 0afdd61..b3e50a6 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -286,6 +286,8 @@
     memcpy( dst, src, sizeof( mbedtls_ssl_session ) );
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
+
+#if defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
     if( src->peer_cert != NULL )
     {
         int ret;
@@ -304,8 +306,7 @@
             return( ret );
         }
     }
-
-#if !defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)
+#else /* MBEDTLS_SSL_KEEP_PEER_CERTIFICATE */
     if( src->peer_cert_digest != NULL )
     {
         dst->peer_cert_digest_len = src->peer_cert_digest_len;