[Bug]: Restore mode on data fingerprint changes try to hydrate files missing from server

[mgallien]

⚠️ Before submitting, please verify the following: ⚠️

• This is a bug, not a question or a configuration issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
• I agree to follow Nextcloud's Code of Conduct

Bug description

When a client detects a change on the data fingerprint reported by the server, it switches to restore mode.
If the server is missing a file that is a virtual one on the client side, the client will try to upload it again. That will trigger implicit hydration of it during attempt to upload it.
That file being missing on the server prevents hydration.
Then the client is going to be infinitely be stuck in a continuous loop trying to upload a non existing file.

Steps to reproduce

1. Have a file be a placeholder (virtual file without data)
2. Change the data fingerprint on the server
3. Delete the file on the server
4. Try to sync with the client
5. Client should delete the lost file and successfully sync the new data fingerprint

Expected behavior

Client should delete the lost file and successfully sync the new data fingerprint

Which files are affected by this bug

n/a

Operating system

Windows

Which version of the operating system you are running.

Windows 10 / Windows 11

Package

Other

Nextcloud Server version

27.0.1

Nextcloud Desktop Client version

3.10.0

Is this bug present after an update or on a fresh install?

Updated from a minor version (ex. 3.4.2 to 3.4.4)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

No response

Additional info

No response

[mgallien]

already done see #5498