[Bug] Not selecting code block language makes crepe.getMarkdown() throw due to new blockLatexSchema

[VoloBuilds]

Initial checklist

• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything (or linked relevant results below)

Affected packages and versions

v7.6.1

Link to runnable example

https://crepe-editor-bug-simulator.lovable.app/

Steps to reproduce

1. Install:
   "@milkdown/crepe": "7.6.1"
   "@milkdown/utils": "7.6.1"
2. Create Crepe editor
3. Create a code block and do not specify the language
4. Attempt to call crepe.getMarkdown()

See link for demo (check console log - it points to the new change intended to support latex)
https://crepe-editor-bug-simulator.lovable.app/

Code running that demo:

import { useEffect, useRef } from "react";
import { Crepe } from '@milkdown/crepe';
import { replaceAll, getMarkdown } from '@milkdown/utils';
import "@milkdown/crepe/theme/common/style.css";
import "@milkdown/crepe/theme/frame.css";

export function Editor() {
  const editorRef = useRef<Crepe | null>(null);
  const containerRef = useRef<HTMLDivElement>(null);

  useEffect(() => {
    if (!containerRef.current || editorRef.current) return;

    const crepe = new Crepe({
      root: containerRef.current,
    });

    crepe.create().then(() => {
      editorRef.current = crepe;
      
      // Set some initial content with a code block
      crepe.editor.action(replaceAll(`# Test

\`\`\`
console.log('hello')
\`\`\`
`));
      
      // Try to get markdown content - this will throw if code block has no language
      try {
        const content = crepe.editor.action(getMarkdown());
        console.log('Content:', content);
      } catch (e) {
        console.error('Error getting markdown:', e);
      }
    });

    return () => {
      editorRef.current?.destroy();
    };
  }, []);

  return (
    <div className="h-full flex-1 flex flex-col">
      <div ref={containerRef} className="flex-1 pl-8 p-4 editor-pane" />
    </div>
  );
}

Btw, if you do select a language, it works without any issues. So this is specific to having no language selected in a code block and trying to getMarkdown().

Expected behavior

getMarkdown() should return the markdown despite no language being selected in the code block.

Actual behavior

getMarkdown() throws error in console and does not return the current markdown

Seems directly related to new code for v7.6.1:
18db4dc

Potentially easy fix just to change
if (language.toLowerCase() === 'latex') {
to:
if (language?.toLowerCase() === 'latex') {
(but I'm not familiar enough to be certain)

Btw, thank you for this incredible project!

Runtime

Chrome

OS

Windows

Build and bundle tools

Vite