Fix subfolders in encrypted folders

[daniele-verducci]

How to repro:

• create encrypted folder
• create encrypted subfolder inside the one just created
• app crashes

How to repro 2:

• enter encrypted folder
• enter encrypted subfolder inside the previous one
• app crashes

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI (N/A)

[github-actions]

APK file: https://github.com/nextcloud/android/actions/runs/34505348733/artifacts/10163844801
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)

[github-actions]

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.

[github-actions]

Codacy

SpotBugs

Category	Base	New
Bad practice	35	35
Correctness	58	58
Dodgy code	195	195
Experimental	1	1
Malicious code vulnerability	2	2
Multithreaded correctness	26	26
Performance	37	37
Security	19	19
Total	373	373

[github-actions]

master-IT test failed: https://www.kaminsky.me/nc-dev/android-integrationTests/17608-IT-master-17-26