Empty files attached to requests are not submitted to receiving components

[ba66e77]

[Description of defect]
When an empty, 0-byte file is submitted on a request, that file is listed in the resulting submission as supporting documentation but is not attached to the email sent to the receiving component.

This is admittedly an edge-case as no one should be submitting empty files.

Steps to reproduce the behavior

1. Create a 0-byte file (e.g., touch empty.txt or create text file and save it without putting in any content)
2. Attach the file to a FOIA Request
3. Observe that the email sent to the receiving agency lists the file as submitted documentation but does not have it attached to the email.