Sharing attachment with no comment does not make the attachment visible to customer via the portal

Issue Summary

When adding attachment via the Agent View and when no comment is entered, even though the Agent presses 'Share with customer' button, the attachment does not become visible to customer

Steps to Reproduce

1. Login to JIRA Service Desk 4.5.2 via portal as a customer, create a new case
2. From another browser, login to the same JSD as Agent, locate the case logged by the customer in the step above and upload an attachment either via drag and drop, or via the 'browse' option Don't add any comments, just click "Share with customer" button

Expected Results

The attachment should become visible to customer via the portal

Actual Results

The attachment is not visible

Workaround

Option 1a: For new attachments, add any comment before pressing "Share with customer" button.
Option 1b: For new attachments, add them by opening the ticket from the customer facing view
Option 2: For existing attachments, reference the attachment in a new public comment via the wiki markup [^filename]

Additional notes:

This happens only in JIRA Service Desk 4.5.2 onwards, JSD 4.5.1 doesn't seem to be affected