Owned type change not persisting if original data is null

[RafaelSalguero]

When updating an existing owned type where originally all it's properties are null, the update is not detected by the ChangeTracker, but if a single column is assigned to a not-null value in the database, the update is executed as normally.

Steps to reproduce

• Create an owned type where all of its properties can be null
• INSERT a row with only null values and another with some non-null values
• Updating the owned type property for the all-nulls rows doesn't do anything
• The same code for the 2nd row with some non-null values does update

class MyTable {
 public int IdMyTable { get; set; }
 public MyOwnedType Owned { get; set; } = new MyOwnedType()
}

[Owned]
class MyOwnedType {
  public string Prop1 { get; set; }
  public string Prop2 { get; set; }
}

var row = c.MyTable.Where(x => x.IdMyTable == 1).First();

//This is done on the database only if the original row has any non-null value in owned type related columns
row.Owned.Prop1 = "hello";

//If we inspect the ChangeTracker, 2 entities are tracked for the row with non-nulls but only 1 with the all nulls row
c.SaveChanges();

Further technical details

EF Core version: 3.1.3
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET Core 3.1
Operating system: Windows 10
IDE: Visual Studio 2019 16.5.0

[AndriySvyryd]

Duplicate of #18007
Don't initialize MyTable.Owned in the constructor instead do it in the getter: #20213 (comment)