PVS-Studio warning V564 for wesnoth

enum { REMOVE_EMPTY = 0x01,
       STRIP_SPACES  = 0x02
};

void unit_preview_pane::draw_contents()
{
  ...
  // we don't remove empty lines, so all fields stay
  // at the same place
  const std::vector<std::string> lines =
    utils::split(text.str(), '\n',
      utils::STRIP_SPACES & !utils::REMOVE_EMPTY);
  ...
}

This suspicious code was found in wesnoth project by PVS-Studio static code analyzer.
Warning message is:
V564 The '&' operator is applied to bool type value. You've probably forgotten to include parentheses or intended to use the '&&' operator. wesnoth dialogs.cpp 902

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