Import code snippet with no explicit language breaks subsequent content

[kraenhansen]

Describe the bug

Content cannot proceed the import code snippet if no language is specified.

Minimal reproduction

https://stackblitz.com/edit/github-vvz8b5ao?file=slides.md

Steps to reproduce the behavior:

1. Create file named file-a.js with a single line // Hello from File A
2. Make a simple slide using the import code snippet syntax (without specifying a language) and observe how the render breaks:

# Hi from Test

<<< @/file-a.js

```bash
# Testing
```

Note how the bug goes away if you specific a language when importing:

<<< @/file-a.js js

Environment

• Slidev version: v51.3.0
• Browser: N/A
• OS: N/A

I see this locally and on Stackblitz.