"Open in collectives" from `.attachments` folder leads to "Page not found"

[mejo-]

Describe the bug
The "Show in Files" action in the attachments sidebar tab opens the .attachments.<fileId> folder and there the hint "The content of this folder is best viewed in the Collectives app" is displayed. The "Open in Collectives" button tries to open a page with the .attachments.<fileId> path though, which results in "Page not found."

Expected behavior
We should open the page path without .attachments.<fileId>.