After deleting a file which was uploaded via Form, the same Form becomes inaccessible.
Steps to reproduce:
1. Create a new Form containing File and Button inputs.
2. Upload a new file via this form and submit it.
3. Try to access this file via Back Office.
4. Remove the file (Send to Trash button)
5. Try to access the Form via Back Office.
An exception is thrown:
For further reference, please see attached stacktrace.png.
6. Go to Trash and remove the file permamently.
7. Try to access the Form via Back Office once again
Another exception is thrown: