fix: Prevent DiscoverySingleLocalDirectoryJob from hanging when target is file

[claucambra]

Resolves

#10071

Summary

Should allow the sync process to finish.

Checklist

• Sign-off message is added to all commits.
• The commit history is clean with no merge commits.
  • How to rebase your commits
  • How to squash commits with rebase
• Uploaded screenshots from before and after for UI changes.
• Test(s) added to branch, with before/after results included in PR description, for performance improvements where applicable.
• [] Documentation has been updated or is not required.
• Backports requested where applicable (critical bugfixes).
• Labels added where applicable (bug/enhancement).
• Milestone added for target version.

AI (if applicable)

• The content of this PR was partly or fully generated using AI
  • I have read the guidelines for AI-assisted contributions.
  • I have read Nextcloud's AI Contribution Policy.

[camilasan]

@claucambra you just need to fix the compilation of the test on Windows.

[claucambra]

/backport to stable-34.0 please

[github-actions]

Artifact containing the AppImage: nextcloud-appimage-pr-10434.zip

Digest: sha256:1fd9dbd9e5df08e36963d724e379ea42061795582564ec2300a288605888df37

To test this change/fix you can download the above artifact file, unzip it, and run it.

Please make sure to quit your existing Nextcloud app and backup your data.

[sonarqubecloud]

Quality Gate failed

Failed conditions
E Maintainability Rating on New Code (required ≥ A)
1 New Bugs (required ≤ 0)
E Reliability Rating on New Code (required ≥ A)
33 New Code Smells (required ≤ 0)

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