NullReferenceException：对象引用未设置为对象实例错误，尝试在VRChat中上传头像时出现了该错误。如何修复？

我试图上传一个旧的头像到VRChat，因为它已经不再存在游戏中，但我却不断遇到这个错误，我对Unity一无所知，也找不到解决这个问题的特别解决方案。请帮忙，我只想和小家伙一起玩lol

全错误：NullReferenceException：对象引用不为null

VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder+<>c.b__100_0(System.String selected) (在./Packages/com.vrchat.avatars/Editor/VRCSDK/SDK3A/VRCSdkControlPanelAvatarBuilder.cs:1541)

UnityEngine.UIElements.PopupField`1[T].GetValueToDisplay () (在<332857d8803a4878904bcf8f9581ec33>:0)

UnityEngine.UIElements.BasePopupField`2[TValueType,TValueChoice].SetValueWithoutNotify (TValueType newValue) (在<332857d8803a4878904bcf8f9581ec33>:0)

UnityEngine.UIElements.PopupField`1[T].SetValueWithoutNotify (T newValue) (在<332857d8803a4878904bcf8f9581ec33>:0)

UnityEngine.UIElements.BaseField`1[TValueType].set_value (TValueType value) (在<332857d8803a4878904bcf8f9581ec33>:0)

UnityEngine.UIElements.PopupField`1[T].set_value (T value) (在<332857d8803a4878904bcf8f9581ec33>:0)

VRC.SDK3A.Editor.VRCSdkControlPanelAvatarBuilder.HandleAvatarSwitch (UnityEngine.UIElements.VisualElement root) (在./Packages/com.vrchat.avatars/Editor/VRCSDK/SDK3A/VRCSdkControlPanelAvatarBuilder.cs:1740)

System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.b__7_0 (System.Object state) (在<27124aa0e30a41659b903b822b959bc7>:0)

UnityEngine.UnitySynchronizationContext+WorkRequest.Invoke () (在:0)

UnityEngine.UnitySynchronizationContext.Exec () (在:0)

UnityEngine.UnitySynchronizationContext.ExecuteTasks () (在:0)