Fix: NotFoundException for anonymous users

[Koc]

• Resolves: OCP\Files\NotFoundException thrown when a file is submitted via link share and user is not logged in forms#2435

• Follow-up of fix(files_versions): Check for user and owner before call getUserFolder #41749

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[come-nc]

/backport to stable31

[come-nc]

/backport to stable30

[come-nc]

/backport to stable29

[susnux]

Is this not a deeper problem @come-nc ?
So this method is not marked as throwing, but just to return null if not found.
Meaning should we fix the getOwner method or at least add the throwing to the docs?

[come-nc]

This is how we manage non-existing files, see https://github.com/nextcloud/server/blob/master/lib/private/Files/Node/NonExistingFile.php

We could mark all methods as throwing but that would trigger a lot of false positive.

[come-nc]

Actually for getOwner the throw comes from Node::getFileInfo directly I think.

[susnux]

But in this case the file exists

[come-nc]

No it does not.
Look at the trace in nextcloud/forms#2435
It’s triggered by rename hook, so either source or target does not exist, depending if we are in the pre- or post- rename hook/event.