When a User (for example Anonymous User) does not have permission to read the form's File upload directory, a notification email containing submissions detail will have the "file" field empty.

Steps to reproduce
1. Clean installation of Ibexa DXP v3.3+ with swift mailer configured
2. In the back office remove the "form" section from Anonymous User's content/read permission.
3. Create a new form at the root of Content Structure:
1. Field: file
2. Field: button (notification: <your-email-addreess>)
4. Open the previously created form in frontend Siteaccess and submit it providing a file.
5. Check email provided in step 3 for the notification email

Result
The notification email will have an empty file field value.

Expected result
The notification email will have the file field value displayed correctly.