Preview not working

The preview does not work in either semantic or bootstrap themes. It always goes to "Nothing to preview"

This was working for me in older versions.

## Details
- OS (Operating System) version: Linux
- Browser and browser version: chrome
- Django version: 5.1
- Martor version & theme: 1.6.45 semantic and bootstrap

### Steps to reproduce

1. use the AdminMartorWidget to override models.TextField
2. view admin

Any ideas why this is the case?

Reproduce the issue in the Django admin using AdminMartorWidget with the semantic and Bootstrap themes, Django 5.1, and Chrome on Linux. Start by tracing the preview behavior from the widget, then verify that entering content renders a preview instead of “Nothing to preview” in both themes.

Scritto dal modello di indicizzazione a partire dal testo della issue.