Useless foldout in Dictionary

[Roy Ng]

1. What happened?
   Always show the foldout in Dictionary, such as class and AnimationCurve, but it’s useless action.

2. How can we reproduce it?
   Use component below

   ``` public class Test : SerializedMonoBehaviour { public Dictionary<string, Child> dict = new Dictionary<string, Child>();

   [System.Serializable]
   public class Child
   {
       public string name;
       public AnimationCurve curve = new AnimationCurve { };
       public int value;
   }
   

   } ```

3. If screenshots would help explain or demonstrate your issue, please include these.

   

4. What version of Unity are you using?
   2021.3.16f1

5. What version of Odin are you using? (See "Tools > Odin Inspector > About")
   3.1.9.0
6. Do you have Editor Only mode enabled?
   No (Odin serializer Enabled)
7. What operating system are you on?
   Windows 10‌

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