Bug 853615

Description of problem:

      Recenly,I 'm  developing a HA test program. I used openais's lck as core module,and cooperated with evt and ckpt modules.
      desing  theory:When a lock is locked or unlocked in a client,it will immediately send a evevnt to all. 
      Now   program's  basic function is normal.But When I do same abnormal test,I find several segmentation fault.

Version-Release number of selected component (if applicable):
ver:openais-0.80.6
modules:lck,evt,ckpt

How reproducible:
see "Steps to Reproduc"

Steps to Reproduce:
1.start aisexec process
2.start client process,now some node get lock.
3.I intentionally kill aisexec server in lock owner node,and the client  will  send a evevt notice.Then  Client crashed with a  a segmentation fault.

Actual results:
Client crashed with a segmentation fault.

Expected results:
Cliet don't crash.

Additional info:
position and my solutions.
SaAisErrorT
saEvtDispatch(
	SaEvtHandleT evtHandle,
	SaDispatchFlagsT dispatchFlags)
{
 ......
            basic function
		case MESSAGE_RES_EVT_AVAILABLE:
			evti->ei_data_available = 0;
 
 			pthread_mutex_lock(&evti->ei_response_mutex);

                        //begin add solve  
                        if(NULL == evt)
                        {
                            error = SA_AIS_ERR_LIBRARY;	
			    goto dispatch_unlock;
                        }
                        //end

			evt_recv_event(evti->ipc_ctx, &evt);       // segmentation fault in here
 			pthread_mutex_unlock(&evti->ei_response_mutex);

			if (evt->led_head.error == SA_AIS_ERR_NOT_EXIST) {
				error = SA_AIS_OK;
				break;
			}
......
}