Turned of CS8618 due to incomplete implementation until later in the chatper
MODIFY
src/Chapter12/Listing12.13.InitializingAFieldWithTheDefaultOperator.cs
src/Chapter12/Listing12.13.InitializingAFieldWithTheDefaultOperator.cs
+// Justification: Only showing partial implementaiton.
+#pragma warning disable CS8618 // Non-nullable field is uninitialized. Consider declaring as nullable.
+
namespace AddisonWesley.Michaelis.EssentialCSharp.Chapter12.Listing12_13
{
using Listing12_08;

Turned of CS8618 due to incomplete implementation until later in the chatper