Optimize handler_stats_disable() when handler_stats are already disabled

MDEV-33502 Slowdown when running nested statement with many partitions

sql/handler.h

@@ -3456,6 +3456,7 @@ class handler :public Sql_alloc
                ("handler created F_UNLCK %d F_RDLCK %d F_WRLCK %d",
                 F_UNLCK, F_RDLCK, F_WRLCK));
     reset_statistics();
+    active_handler_stats.active= 0;
   }
   virtual ~handler(void)
   {
@@ -4877,9 +4878,12 @@ class handler :public Sql_alloc
   }
   inline void ha_handler_stats_disable()
   {
-    handler_stats= 0;
-    active_handler_stats.active= 0;
-    handler_stats_updated();
+    if (handler_stats)
+    {
+      handler_stats= 0;
+      active_handler_stats.active= 0;
+      handler_stats_updated();
+    }
   }
 
 private: