procedure TTileDownloaderSimple.OnConfigChange;

var

  VTileDownloaderConfigStatic: ITileDownloaderConfigStatic;

begin

  VTileDownloaderConfigStatic := FTileDownloaderConfig.GetStatic; // <- AV

  ...

procedure TNotifierBase.Notify(const AMsg: IInterface);

var

  idx: Integer;

  VList: array of IListener;

begin

  FSync.BeginRead;

  try

    SetLength(VList, FListeners.Count);

    for idx := 0 to FListeners.Count - 1 do begin

      VList[idx] := IListener(Pointer(FListeners[idx]));

    end;

  finally

    FSync.EndRead;

  end;

  for idx := 0 to Length(VList) - 1 do begin

    VList[idx].Notification(AMsg);

    VList[idx] := nil;

  end;

  VList := nil;

end;