Full work only cast Emun to object

Author: DocSvartz

src/Mapster.Tests/WhenMappingNullableEnumRegression.cs

@@ -19,9 +19,16 @@ public void NullEnumToNullClass()
 
             MyClass myClass = new() { TypeEmployer = MyEnum.User };
 
+            MyClass myClassNull = new() { TypeEmployer = null};
+
+
             var _result = myClass?.Adapt<MyDestination?>(); // Work
 
+            var _resultNull = myClassNull.Adapt<MyDestination>(); // Null Not Error When (object)s if (MyEnum)s - NullReferenceException
+
             _result.TypeEmployer.Key.ShouldBe(MyEnum.User.ToString());
+
+            _resultNull.TypeEmployer.ShouldBeNull();
         }
 
         /// <summary>

src/Mapster/Utils/ExpressionEx.cs

@@ -312,11 +312,11 @@ public static Expression NullableEnumExtractor(this Expression param)
 
             if (_SourceType.IsNullable())
             {
-                var _genericType = param.Type.GetGenericArguments()[0]!;
+                var _genericType = param.Type.GetGenericArguments()[0];
 
                 if (_genericType.IsEnum)
                 {
-                    var ExtractionExpression = Expression.Convert(param, _genericType);
+                    var ExtractionExpression = Expression.Convert(param, typeof(object));
                     return ExtractionExpression;
                 }