MDEV-10045: Server crashes in Time_and_counter_tracker::incr_loops

Do not set 'optimized' flag until whole optimization procedure is finished.

sql/sql_select.cc

@@ -1073,6 +1073,7 @@ JOIN::optimize_inner()
   DBUG_ENTER("JOIN::optimize");
 
   do_send_rows = (unit->select_limit_cnt) ? 1 : 0;
+
   DEBUG_SYNC(thd, "before_join_optimize");
 
   THD_STAGE_INFO(thd, stage_optimizing);