Issue Summary

This is reproducible on Data Center: (yes)

The issue only happens in Jira Service Management Projects, as it's the only version of Jira that adds an attachment while commenting on another popup.

Steps to Reproduce

1. Add a Comment on an Issue
2. During the add comment, add an attachment
3. During the add attachment, press cancel.
4. It will pop up a screen, to confirm canceling the adding of the attachment: "Your files were not attached. Are you sure you want to cancel?"
5. In the comment text box, you will see a link to a reference for an attachment that is not there.

Expected Results

do not show any reference to a nonexisting attachment.

As it is working on the Jira Software project.

Actual Results

On the comment text box, you get a link reference to a none existing attachment,
something like:

the link addres is something like: blob:http://localhost:8080/3b68c730-736e-4a71-a608-6efeda444b1d

Workaround

If the user cancels the attachments, he needs to delete the reference to the none existing attachment.