Quill is not working with vuejs and showing arrow image

I've followed the quill playground guide but using vuejs and it doesn't work. There's no error on the browser but a weird arrow is showing.

Example: https://codepen.io/danny1014/pen/gOLZNZQ

var quill = new Quill("#quill-container", {
  modules: {
    toolbar: [
      [{ header: [1, 2, false] }],
      ["bold", "italic", "underline"],
      ["image", "code-block"]
    ]
  },
  scrollingContainer: "#scrolling-container",
  placeholder: "Compose an epic...",
  theme: "bubble"
});