Invalid Code for `concat` function in `src/utils/innerSliderUtils.js`

[Flcwl]

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Why using the concat function? it's like invalid writing in https://github.com/akiran/react-slick/blob/master/src/utils/innerSliderUtils.js

  // in line:136.
  lazyLoadedList.concat(slidesToLoad);

  // in line:225.
 lazyLoad &&
      lazyLoadedList.concat(
        getOnDemandLazySlides({ ...spec, currentSlide: animationSlide })
      );