Unity 5.1 Import settings Problem

When i set filter mode in import settings window and after pressing apply, Error occurred. but if i set filter mode in unity 5.0, it works fine. how to fix it? below is full error. sorry for my english.

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.SpriteEditorWindow.ApplyCacheSettingsToInspector (UnityEditor.SerializedObject so) (at C:/buildslave/unity/build/Editor/Mono/SpriteEditor/SpriteEditorWindow.cs:143)
UnityEditor.SpriteEditorWindow.TextureImporterApply (UnityEditor.SerializedObject so) (at C:/buildslave/unity/build/Editor/Mono/SpriteEditor/SpriteEditorWindow.cs:138)
UnityEditor.TextureImporterInspector.Apply () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/TextureImporterInspector.cs:2201)
UnityEditor.AssetImporterInspector.ApplyAndImport () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/AssetImporterInspector.cs:148)
UnityEditor.AssetImporterInspector.ApplyButton (System.String buttonText) (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/AssetImporterInspector.cs:199)
UnityEditor.AssetImporterInspector.ApplyButton () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/AssetImporterInspector.cs:192)
UnityEditor.AssetImporterInspector.ApplyRevertGUIButtons () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/AssetImporterInspector.cs:210)
UnityEditor.AssetImporterInspector.ApplyRevertGUI () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/AssetImporterInspector.cs:226)
UnityEditor.TextureImporterInspector.OnInspectorGUI () (at C:/buildslave/unity/build/Editor/Mono/ImportSettings/TextureImporterInspector.cs:1329)
UnityEditor.InspectorWindow.DrawEditor (UnityEditor.Editor editor, Int32 editorIndex, Boolean forceDirty, System.Boolean& showImportedObjectBarNext, UnityEngine.Rect& importedObjectBarRect, Boolean eyeDropperDirty) (at C:/buildslave/unity/build/Editor/Mono/Inspector/InspectorWindow.cs:1162)
UnityEditor.DockArea:OnGUI()

I’m having the exact same problem, although, I didn’t know it works fine in 5.0 . I suppose I’ll stick with it until the problem is fixed :c

Close your sprite editor window. It worked for me.

I am having this problem too.