Fails to install Fancy Zones on latest version of Linux Mint

Here's the log after clicking **Fancy Zones** `(Install)` button
```
~/bin> LinuxPowerToys-0.8-x86_64.AppImage
Gtk-Message: 14:07:59.231: Failed to load module "xapp-gtk3-module"
flutter: [SEVERE] 2025-05-13 14:08:01.588990: Failed to get 'inner-gaps' setting
[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: GSettings schema org.gnome.shell.extensions.tilingshell not installed
#0 GSettings._load (package:gsettings/src/gsettings.dart:192)

#1 new GSettings.. (package:gsettings/src/gsettings.dart:98)

flutter: [SEVERE] 2025-05-13 14:08:01.589788: Failed to get 'enable-span-multiple-tiles' setting
flutter: [SEVERE] 2025-05-13 14:08:01.590675: Failed to get 'enable-snap-assist' setting
flutter: [SEVERE] 2025-05-13 14:08:01.590760: Failed to get 'layouts-json' setting
flutter: [SEVERE] 2025-05-13 14:08:01.590832: Failed to get 'outer-gaps' setting
flutter: [SEVERE] 2025-05-13 14:08:01.590875: Failed to get 'layouts-json' setting
[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: RangeError (length): Invalid value: Valid value range is empty: 0
#0 GnomeFancyZonesBackend.install (package:linuxpowertoys/src/backend_api/utilities/fancy_zones/gnome_fancy_zones_backend.dart)

#1 _FancyZonesScreenState.handleInstallPressed. (package:linuxpowertoys/src/screens/fancy_zones/fancy_zones_screen.dart:99)

flutter: [SEVERE] 2025-05-13 14:24:13.224713: Failed to get 'outer-gaps' setting
flutter: [SEVERE] 2025-05-13 14:24:13.224772: Failed to get 'layouts-json' setting
flutter: [SEVERE] 2025-05-13 14:24:13.224789: Failed to get 'enable-span-multiple-tiles' setting
flutter: [SEVERE] 2025-05-13 14:24:13.224816: Failed to get 'enable-snap-assist' setting
flutter: [SEVERE] 2025-05-13 14:24:13.224831: Failed to get 'layouts-json' setting
flutter: [SEVERE] 2025-05-13 14:24:13.224842: Failed to get 'inner-gaps' setting
[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: GSettings schema org.gnome.shell.extensions.tilingshell not installed
#0 GSettings._load (package:gsettings/src/gsettings.dart:192)

#1 new GSettings.. (package:gsettings/src/gsettings.dart:98)

```

Start with package/linuxpowertoys/src/backend_api/utilities/fancy_zones/gnome_fancy_zones_backend.dart and the call from package/linuxpowertoys/src/screens/fancy_zones/fancy_zones_screen.dart:99. Reproduce the Fancy Zones installation on the reported Linux Mint setup and inspect how the missing GSettings schema and empty values are handled. Done means clicking Install completes without an unhandled exception and Fancy Zones is installed.

Written by the indexing model from the issue text.