App crashes when syncing a project with a virtual layer after .qgz file is updated

Description

When a project containing a QGIS virtual layer is open in the mobile app, syncing a change that includes an updated .qgz project file causes the app to crash. Syncing data-only changes (no .qgz update) works correctly.

Environment
[ ] Staging [x] PROD

Application (+ app version, build, operating system)

• Mergin Maps mobile 2026.2.0, Android 9 (Samsung Galaxy Tab S3), Android 16 (Pixel)
• Mergin Maps mobile 2026.2.0, iOS 26.0

Steps to reproduce

1. Open a project containing a QGIS virtual layer in the mobile app (e.g. tester-ws-1/test_virtual_layer)
2. In QGIS, open the same project, make a change to the .qgz file (e.g. layer visibility or project settings), save and sync to the server
3. In the mobile app, trigger sync
4. The app applies the incoming .qgz update

Actual results

• The app crashes immediately when applying the synced .qgz project file update
• After reopening the app, the synced changes are present (data was written successfully before the crash)

Expected results

The app should reload the updated project without crashing.

Notes

• If the sync contains only data changes (no .qgz update), sync completes successfully
• Issue is specific to projects containing a QGIS virtual layer
• Reproducible across all tested devices and platforms

Screenshots or logs

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Conclusion
Created by Claude and supervised by a human test analyst.