Avoid unnecessary allocations on DependencyObjectExtensions.RegisterDisposableNestedPropertyChangedCallback

[pictos]

Overview

On the RegisterDisposableNestedPropertyChangedCallback we allocate an array and a SerialDisposable even when they aren't used. Moving the allocation inside the if will make sure we just allocate then if needed.

Not sure if will be a case where that if will be false, if don't feel free to close this PR.

PR Type

What kind of change does this PR introduce?

• Improvements

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Docs have been added/updated
• Runtime Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Associated with an issue (GitHub or internal)
• Commits must be following the Conventional Commits specification.

Other information

Internal Issue (If applicable):

[github-actions]

Azure Static Web Apps: Your stage site is ready! Visit it here: https://polite-field-01aa64f0f-705.eastus2.azurestaticapps.net

[agneszitte]

@Mergifyio backport legacy/3x

[mergify]

backport legacy/3x

✅ Backports have been created

• #711 Avoid unnecessary allocations on DependencyObjectExtensions.RegisterDisposableNestedPropertyChangedCallback (backport #705) has been created for branch legacy/3x