Can not add snippet

**Describe the bug**
Add snippet by creating new or dragging, console raise an error:
<img width="531" alt="image" src="https://github.com/jupytercalpoly/jupyterlab-code-snippets/assets/17139670/c9aeffd2-039b-4437-87d1-c12097a5a953">

1. Installed in Extension Manager, get a blank panel.
2. Remove the Extension Manager version
3. Installed by pip
4. Panel appears, but can not add.
