[stable33] fix: correctly return false for filesize on non-existing file

[backportbot]

Backport of #58543

Warning, This backport's changes differ from the original and might be incomplete ⚠️

Todo

• Review and resolve any conflicts
• Amend HEAD commit to remove the line stating to skip CI

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[icewind1991]

/backport! to stable32

[backportbot]

The backport to stable32 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable32
git pull origin stable32

# Create the new backport branch
git checkout -b backport/58553/stable32

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 276ca39a e88748e7

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/58553/stable32

Error: Failed to push branch backport/58553/stable32: remote: Invalid username or token. Password authentication is not supported for Git operations.
fatal: Authentication failed for 'https://github.com/nextcloud/server.git/'

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.