Merge pull request #1849 from haoyifan/timer_fix

[Timer] Initialize the last tmrCtrls.

src/util/src/ttimer.c

@@ -501,6 +501,7 @@ static void taosTmrModuleInit(void) {
     tmr_ctrl_t* ctrl = tmrCtrls + i;
     ctrl->next = ctrl + 1;
   }
+  (tmrCtrls + taosMaxTmrCtrl - 1)->next = NULL;
   unusedTmrCtrl = tmrCtrls;
 
   pthread_mutex_init(&tmrCtrlMutex, NULL);