Activity stream link to a pinned comment on older attachment version will lead to a greyed page

Summary

When a user leaves a pinned comment in an attachment, one entry will be added in the activity stream. If someone uploads a newer version of the attachment to the same page, that entry will be broken. Clicking on the link will lead the user to a greyed page, as if the preview was not being properly loaded.

Steps to reproduce

1. Attach a PDF file to a page.
2. Preview the file and leave a pinned comment on it.
3. Attach another PDF file with the same name, so that Confluence considers "Version 2".
4. Go to the Dashboard or any page with an Activity Stream macro.
5. Click the link referring to the pinned comment from step 2.

Expected Results

Confluence should preview the older file and highlight the pinned comment.

Actual Results

The opaque grey screen from the file preview window appears, but no file is shown.