Why I am getting an error of "Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory "

Question

I am getting an error message of Warning: Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.

I have used the cleanUp in useState but still I am getting error.

Here is the code:

    let isComponentMounted = useRef(false);
  
  useEffect(()=>{
    isComponentMounted.current = true;
    setLoading(true);

    if(isComponentMounted){
      async function  fetchData(){
        const data = await fetch(`/data`) 
        const res = await data.json();
        setLoading(false);
        return res
      }
    
      fetchData().then((response)=>{
        setMovie(response.data.movies[Math.floor(Math.random()*response.data.movies.length-1)])
      })
    }


    return()=>{isComponentMounted.current = false; setMovie()}
  },[])

I am new to react it would be really helpful