VNode.data can be undefined and should be used normally

[DM|全渣攻城獅]

import {
  init,
  classModule,
  styleModule,
  eventListenersModule,
  h,
  vnode,
} from "../../build/index.js";

const patch = init(
  [classModule, styleModule, eventListenersModule],
  undefined,
  { experimental: { fragments: true } }
);
const container = document.getElementById("container");
const render = () => {
  const patched = patch(
    container,
    vnode(
      undefined,
      undefined,
      [
        vnode("h1", undefined, undefined, "hello", undefined),
        vnode("h1", undefined, undefined, "snabbdom", undefined),
      ],
      undefined,
      undefined
    )
  );
  console.log(patched);
};
render();

throw an error:

class.ts:11 Uncaught TypeError: Cannot read properties of undefined (reading 'class')
    at Array.updateClass (class.ts:11)
    at createElm (init.ts:176)
    at createElm (init.ts:205)
    at patch (init.ts:431)
    at render (index.js:36)
    at index.js:52