Optimistic update on infinite query

// List of posts
export default function ListPage(){
  const router = useRouter()
  const q = router.query.q as string || ''
  const {data} = api.post.feed.useInfiniteQuery({q}, {
        getNextPageParam: lastPage => lastPage.nextCursor,
    })
  const posts = data?.pages.flatMap(page => page.items)

  return (
  <>
     {posts.map(post => <Post post={post}/> )}
  </>
)
}

    const utils = api.useContext()
    const toggleLikeMutation = api.post.toggleLikePost.useMutation({
        onMutate: async () => {
            const snapshot = utils.post.feed.getInfiniteData({q: ''}) 
            console.log({snapshot}) // <---- EMPTY
            if (!snapshot) return {snapshot}
            utils.post.feed.setInfiniteData({}, () => {
                return {
                    ...snapshot,
                    pages: snapshot.pages.map(page => {
                        return {
                            ...page,
                            items: page.items.map(post => {
                                if (post.id !== id) return post
                                return {
                                    ...post,
                                    liked: !post.liked
                                }
                            })
                        }
                    })
                }
            })
            return {
                snapshot
            }
        },

        onError: (error, {postId}, ctx) => {
            ctx?.snapshot && utils.post.feed.setInfiniteData({}, () => ctx.snapshot)
        },

        async onSuccess() {
            await utils.post.feed.invalidate()

        }
    })