[unity] Fixed Exception at SetIconForObject with Unity 2021.2. Closes #2141.

spine-unity/Assets/Spine/Editor/spine-unity/Editor/Components/SkeletonUtilityInspector.cs

@@ -31,6 +31,10 @@
 #define NEW_PREFAB_SYSTEM
 #endif
 
+#if UNITY_2021_2_OR_NEWER
+#define PUBLIC_SET_ICON_FOR_OBJECT
+#endif
+
 using System.Reflection;
 using UnityEditor;
 using UnityEngine;
@@ -145,11 +149,14 @@ namespace Spine.Unity.Editor {
 					icon = Icons.constraintNib;
 					break;
 				}
-
+#if PUBLIC_SET_ICON_FOR_OBJECT
+			EditorGUIUtility.SetIconForObject(boneComponent.gameObject, icon);
+#else
 			typeof(EditorGUIUtility).InvokeMember("SetIconForObject", BindingFlags.InvokeMethod | BindingFlags.Static | BindingFlags.NonPublic, null, null, new object[2] {
 				boneComponent.gameObject,
 				icon
 			});
+#endif
 		}
 
 		static void AttachIconsToChildren (Transform root) {