Guest appears as the last author of a page after modifying attachments with Collabora connector

[lucaa]

How to reproduce:

• upload an office file as an attachment on a page
• edit the office file with collabora
• save the file from collabora
• back in XWiki a new version of the page was added to the page's history with the attachment modification

Expected result:

• the last author of the page in XWiki (for this new history entry) is the current connected user

Actual result:

• the last author of the page in XWiki (for this new history entry) is the Guest