PVS-Studio warning V530 for wesnoth

gui::dialog_button_action::RESULT
delete_recall_unit::button_pressed(int menu_selection)
{
  const std::vector<std::pair<int, int> >& param =
    std::vector<std::pair<int, int> >();
  param.back();
  const size_t index = size_t(filter_.get_index(menu_selection));
  ...
}

It's strange that the result of calling the param.back() function is not used in any way.

This suspicious code was found in wesnoth project by PVS-Studio static code analyzer.
Warning message is:
V530 The return value of function 'back' is required to be utilized. wesnoth menu_events.cpp 91

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