NullReferenceException: (null)
UnityEditor.SerializedObject..ctor (UnityEngine.Object[] objs) (at C:/buildslave/unity/build/Editor/Mono/SerializedObject.cs:21)
UnityEditor.Experimental.AssetImporters.AssetImporterEditor.GetSerializedObjectInternal () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/AssetImporterEditor.cs:73)
UnityEditor.Editor.get_serializedObject () (at C:/buildslave/unity/build/Editor/Mono/Inspector/Editor.cs:433)
UnityEditor.BaseAssetImporterTabUI.get_serializedObject () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/BaseAssetImporterTabUI.cs:13)
UnityEditor.ModelImporterModelEditor.OnEnable () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/ModelImporterModelEditor.cs:48)
UnityEditor.AssetImporterTabbedEditor.OnEnable () (at C:/buildslave/unity/build/Editor/Mono/Inspector/TabbedEditor.cs:83)
UnityEditor.ModelImporterEditor.OnEnable () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/ModelImporterEditor.cs:17)

ゲーム起動時に毎回このようなエラーが出るのですが、どこに原因があるのかわかりません。
どこを確認すればいいのか教えていただけませんか？