null source member should overwrite exsting destination member

Author: lbargaoanu

src/AutoMapper/Execution/ExpressionBuilder.cs

@@ -73,8 +73,7 @@ public static Expression MapExpression(this IGlobalConfiguration configuration,
         bool nullCheck;
         if (typeMap != null)
         {
-            var allowNull = memberMap?.AllowNull;
-            nullCheck = !typeMap.HasTypeConverter && allowNull.HasValue && allowNull != profileMap.AllowNullDestinationValues;
+            nullCheck = !typeMap.HasTypeConverter;
             if (!typeMap.HasDerivedTypesToInclude)
             {
                 typeMap.Seal(configuration);

src/UnitTests/NullBehavior.cs

@@ -1,5 +1,34 @@
 namespace AutoMapper.UnitTests.NullBehavior;
-
+public class NullToExistingValue : AutoMapperSpecBase
+{
+    private record Person
+    {
+        public string Name { get; set; }
+        public Address TheAddress { get; set; } = new();
+    }
+    private record Address
+    {
+        public string Street { get; set; }
+        public int Number { get; set; }
+    }
+    private record PersonModel
+    {
+        public string Name { get; set; }
+        public AddressModel TheAddress { get; set; }
+    }
+    private record AddressModel
+    {
+        public string Street { get; set; }
+        public int Number { get; set; }
+    }
+    protected override MapperConfiguration CreateConfiguration() => new(c =>
+    {
+    	c.CreateMap<PersonModel, Person>();
+    	c.CreateMap<AddressModel, Address>();
+    });
+    [Fact]
+    public void Should_overwrite() => Mapper.Map(new PersonModel(), new Person()).TheAddress.ShouldBeNull();
+}
 public class NullCheckDefault : AutoMapperSpecBase
 {
     class Source