Fix reload when nullable complex property is null

[thromel]

Summary

Reloading an entity with a nullable complex property set to null in the store could throw a conceptual-null error when the complex contained required members. The store value projection was reading non-nullable value types, losing nulls and causing the complex to be treated as non-null.

Fix

• Preserve nulls for value-type members inside nullable complex properties when projecting store values.
• Compute nullable-complex null flags from store values and pass them into ArrayPropertyValues so reload skips nested required members when the complex is null.
• Add regression coverage for reload on optional complex properties.

Closes issue when merged

• Fixes EF 10: EntityEntry.ReloadAsync throws when nullable complex property is null #37559

Test Plan

• Sqlite: reload optional complex property with null store values (PropertyValuesSqliteTest / Reloading_optional_complex_property_with_null_does_not_throw)
• InMemory: reload optional complex property with null store values (PropertyValuesInMemoryTest / Reloading_optional_complex_property_with_null_does_not_throw)
• SqlServer: reload optional complex property with null store values (PropertyValuesSqlServerTest / Reloading_optional_complex_property_with_null_does_not_throw)

ORCID

• https://orcid.org/0009-0009-2432-8960

[Copilot]

Pull request overview

This PR fixes a bug where reloading an entity with a nullable complex property set to null in the database would throw an InvalidOperationException about required members, even when the complex property itself is optional. The root cause was that store value projections were reading non-nullable value types (e.g., int instead of int?), losing null information and causing the complex property to be incorrectly treated as non-null during reload.

Changes:

• Modified store value projection to preserve nulls for value-type members inside nullable complex properties
• Enhanced ArrayPropertyValues to compute null complex property flags from store values
• Added comprehensive regression tests for reloading optional complex properties with null values

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
test/EFCore.Specification.Tests/PropertyValuesTestBase.cs	Added test for reloading optional complex property with null store values and updated seed data to include Building Two with null OptionalMilk
src/EFCore/Internal/EntityFinder.cs	Modified BuildProjection to convert value types to nullable when inside nullable complex properties, preserving null information from database
src/EFCore/ChangeTracking/Internal/ArrayPropertyValues.cs	Added new constructor overload and CreateNullComplexPropertyFlags method to compute null complex property flags from store values
src/EFCore/ChangeTracking/EntityEntry.cs	Updated GetDatabaseValues and GetDatabaseValuesAsync to use new constructor that computes null flags from returned value buffer

[AndriySvyryd]

Thanks for your contribution!