initialize all fields of the struct (it's generally good idea even though they should not be used)

main/output.c

@@ -430,6 +430,8 @@ static int php_ob_init_named(uint initial_size, uint block_size, char *handler_n
 	tmp_buf.chunk_size = chunk_size;
 	tmp_buf.status = 0;
 	tmp_buf.internal_output_handler = NULL;
+	tmp_buf.internal_output_handler_buffer = NULL;
+	tmp_buf.internal_output_handler_buffer_size = 0;
 	tmp_buf.handler_name = estrdup(handler_name&&handler_name[0]?handler_name:OB_DEFAULT_HANDLER_NAME);
 	tmp_buf.erase = erase;