Fails to detect installed Distrobox if bundled version is deleted

[City-busz]

Describe the bug
When I launch DistroShelf, it shows that Distrobox is not installed, even through it's installed on the system. It happens only if I select the bundled version previously, but then I delete the bundled distrobox from user's folder.

To Reproduce
Steps to reproduce the behavior:

1. Install DistroShelf.
2. Open Preferences, and choose Bundled Version.
3. Close DistroShelf.
4. Install Distrobox natively.
5. Delete the ~/.local/share/distroshelf folder
6. Run DistroShelf again, and see that it marks Distrobox as not found.
7. Run gsettings set com.ranfdev.DistroShelf distrobox-executable 'host'
8. Run DistroShelf again, and see that it detects Distrobox.

Desktop (please complete the following information):

• OS: Arch Linux
• Installation method: native
• App version: 1.5.2
• Distrobox version: 1.8.2.5

Additional context
Console output of natively installed DistroShelf (installed Distrobox is not detected):

$ distroshelf 
2026-08-25T18:00:30.990863Z  INFO distroshelf: Starting DistroShelf application
2026-08-25T18:00:31.294768Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=bundled_distrobox_version
2026-08-25T18:00:31.297219Z  INFO distroshelf::models::main_store: Starting podman events listener
2026-08-25T18:00:31.298540Z  WARN distroshelf::query: Resource fetch failed resource_key=container_runtime error=Container runtime not initialized
2026-08-25T18:00:31.299479Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=distrobox_version
2026-08-25T18:00:31.301357Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=selected_source
2026-08-25T18:00:31.303893Z  WARN distroshelf::models::main_store: distrobox_version not ready; falling back to bare 'distrobox'
2026-08-25T18:00:31.304060Z  INFO distroshelf::backends::distrobox::distrobox: Executing command command=distrobox args=["ls", "--no-color"]
2026-08-25T18:00:31.823092Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=host_distrobox_version
2026-08-25T18:00:31.824297Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=containers
2026-08-25T18:00:31.824840Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=container_runtime
2026-08-25T18:00:32.063906Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=json_terminals
2026-08-25T18:00:32.138731Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=flatpak_terminals
2026-08-25T18:00:32.207561Z  WARN distroshelf::models::main_store: distrobox_version not ready; falling back to bare 'distrobox'
2026-08-25T18:00:32.207666Z  INFO distroshelf::backends::distrobox::distrobox: Executing command command=distrobox args=["ls", "--no-color"]
2026-08-25T18:00:32.289870Z  INFO distroshelf::query: Resource fetch completed successfully resource_key=containers