Issue about dwsXPlatformTimer

[achinastone]

I have mentioned the problem about Timer( May be nil).
The more serious problem is the Timer maybe a invalid value but not nil.

[achinastone]

`
function TdwsXTimerQueue.Add(const AInterval: Cardinal; AEvent : TTimerEvent; const AOnTimer: TWaitOrTimerCallback): THandle;
var
Handle : THandle;
Timer : TdwsXTimer;
Event : epoll_event;
begin
Result := INVALID_HANDLE_VALUE;

Handle := timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK);
if Handle <> THandle(-1) then
begin
Timer := TdwsXTimer.Create;
Timer.Handle := Handle;
Timer.Interval := AInterval;
Timer.OnTimer := AOnTimer;
Timer.Event := AEvent;

  Event.data.ptr := Timer;
  Event.events   := EPOLLIN or EPOLLET;
  if epoll_ctl(_TimerQueuePool.Handle, EPOLL_CTL_ADD, Handle, @Event) <> -1 then
  begin
    if _SetInterval(Handle, AInterval) then
    begin
      _TimersLock.Enter;
       try
          _Timers.Add(Handle, Timer);
       finally
          _TimersLock.Leave;
       end;
       Result := Handle;
    end else Timer.Free;  //if _SetInterval return false then the Timer in the EPOLL will be invalid
  end else
  begin
     __close(Handle);
     Timer.Free;
  end;

end;
end;
`