[Bug] custom shcema error:Cannot create node for paragraph

[dingshaohua-com]

card.ts

import { $node, $remark } from '@milkdown/kit/utils';
import { Editor } from '@milkdown/kit/core';
import { jsonToHtmlAttr } from '@dingshaohua.com/utils';

const cardRemark = $remark('remarkDirective1', function () {
  return function () {
    const that = this;
    return function (tree: any) {
      const transformer = (node: any) => {
        if (!node.children) return;
        const firstChild = node.children.at(0);
        const isCardStart = firstChild.type === 'html' && /^<card/.test(firstChild.value.trim());
        if (isCardStart) {
          const htmlNode = jsonToHtmlAttr(firstChild.value);
          const tree: any = that.parse(htmlNode.node.innerHTML.trim());
          node.children.splice(0, node.children.length, {
            type: 'card-node',
            children: tree.children,
            attrs: htmlNode.attrs,
          });
        }
        node.children.forEach(transformer);
      };
      transformer(tree);
    }
  };
});


const cardSchema = $node('card-node', (ctx) => {
  return {
    group: 'block',
    inline: false,
    atom: false, 
    content: 'block*',
    attrs: {
      title: '',
    },

    toDOM: (node) => {
      return [
        'div',
        {
          class: 'card'
        },
        [
          'div',
          {
            class: 'card-title'
          },
          node.attrs.title,
        ],
        [
          'div',
          {
            class: 'card-content'
          },
          0, 
        ],
      ];
    },

    parseMarkdown: {
      match: (node) => node.type === 'card-node',
      runner: (state, node, type) => {
        state.openNode(type, node.attrs);
        if (node.children) {
          state.next(node.children);
        } else if (node.value) {
          state.addText(node.value as string);
        }
        state.closeNode();
      },
    },
  };
});

export default (editor: Editor) => {
  editor.use(cardSchema).use(cardRemark);
};

markdown content

<card title="这是标题">
**这是**另一个测试卡片
哈哈
## 这是标题
嘻嘻
</card>

get error

my-editor.tsx:122 MilkdownError: [Description]: "Cannot create node for paragraph".
[Attributes]: null.
[Content]: ["card-node(paragraph(strong(\"这是\"), \"另一个测试卡片\\n哈哈\"), heading(\"这是标题\"), paragraph(\"嘻嘻\"))"].