[Settings] [Advanced Paste] Upgrade advanced paste settings safely to fix settings ui crash (#44862)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
This pull request makes a minor fix in the `AdvancedPasteViewModel`
constructor to ensure the correct settings repository is used for null
checking. The change improves code correctness by verifying
`advancedPasteSettingsRepository` instead of the generic
`settingsRepository`.

- Fixed null check to use `advancedPasteSettingsRepository` instead of
`settingsRepository` in the `AdvancedPasteViewModel` constructor for
more accurate validation.
<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [x] Closes: #44835
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
issues) -->
- [x] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [x] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/settings-ui/Settings.UI.Library/AdvancedPasteProperties.cs

@@ -93,11 +93,11 @@ namespace Microsoft.PowerToys.Settings.UI.Library
 
         [JsonPropertyName("custom-actions")]
         [CmdConfigureIgnoreAttribute]
-        public AdvancedPasteCustomActions CustomActions { get; init; }
+        public AdvancedPasteCustomActions CustomActions { get; set; }
 
         [JsonPropertyName("additional-actions")]
         [CmdConfigureIgnoreAttribute]
-        public AdvancedPasteAdditionalActions AdditionalActions { get; init; }
+        public AdvancedPasteAdditionalActions AdditionalActions { get; set; }
 
         [JsonPropertyName("paste-ai-configuration")]
         [CmdConfigureIgnoreAttribute]