my Unity version is 2019.3.0f6
Import attached files and go to animation tab.
Instead of animation clips editing interface it shows only two top checkers and throws errors in console
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.ModelImporterClipEditor.FindNextAvailableName (System.String baseName) (at <6f28216fea9f453abf2e05b770ed3ee4>:0)
UnityEditor.ModelImporterClipEditor.MakeUniqueClipName (System.String name) (at <6f28216fea9f453abf2e05b770ed3ee4>:0)
UnityEditor.ModelImporterClipEditor.AddClip (UnityEditor.TakeInfo takeInfo) (at <6f28216fea9f453abf2e05b770ed3ee4>:0)
UnityEditor.ModelImporterClipEditor.SetupDefaultClips () (at <6f28216fea9f453abf2e05b770ed3ee4>:0)
UnityEditor.ModelImporterClipEditor.OnEnable () (at <6f28216fea9f453abf2e05b770ed3ee4>:0)
UnityEditor.AssetImporterTabbedEditor.OnEnable () (at <6f28216fea9f453abf2e05b770ed3ee4>:0)
UnityEditor.ModelImporterEditor.OnEnable () (at <6f28216fea9f453abf2e05b770ed3ee4>:0)
it seems to be editor UI error.
This happens in fresh project too.
This do not happen in previos unity version.
One article on GitHub suggest that this happends because of version specific code in UnityAPIWrapper, i dont know what does that even means.