TypeError when viewing sent email on v2.1.2

[P4b10Cruz]

Hello,

I'm experiencing a persistent TypeError when trying to view a sent email. The API call to /admin/mail/sent returns a 200 OK status, but the response is an HTML page instead of JSON data, causing the frontend to crash.

Error in Console:
TypeError: Cannot read properties of undefined (reading 'id')

Steps to Reproduce:

1. Go to the "Email" section.
2. Click on the "Sent" folder.
3. Click on any sent email to view its details.
4. The UI fails to load the detail pane and the TypeError appears in the console.

Troubleshooting Steps Taken:

• Correct APP_URL in .env with https.
• Cleared all caches (config, view, route, cache, sessions).
• Corrected all file permissions (chown and chmod).
• Recreated storage link.
• Reinstalled all application files from a fresh v2.1.2 zip.
• Recompiled frontend assets with npm run build on a compatible Node.js version.
• The issue persists even with APP_DEBUG=true (it returns an HTML page, not a debug page).

Thanks,
Pablo