'Files' is possibly null

const fetchPosts=useCallback(async()=>{
  

    const { data:files } = await supabase
    .storage
    .from('files')
    .list()

    for (const file of files) {
      const { data } = await supabase.storage.from('bucket').createSignedUrl(file.name, 600000)
      
    }
  

  },[])