active な mesh が 0 のときに export できないようにする

Assets/VRM/UniVRM/Editor/Format/VRMExporterMenu.cs

@@ -25,6 +25,18 @@ namespace VRM
             wiz.OnWizardUpdate();
         }
 
+        void OnEnable()
+        {
+            // Debug.Log("OnEnable");
+            EditorApplication.hierarchyWindowChanged += OnWizardUpdate;
+        }
+
+        void OnDisable()
+        {
+            // Debug.Log("OnDisable");
+            EditorApplication.hierarchyWindowChanged -= OnWizardUpdate;
+        }
+
         void OnWizardCreate()
         {
             // save dialog

Assets/VRM/UniVRM/Scripts/Format/VRMExportSettings.cs

@@ -83,6 +83,11 @@ namespace VRM
             {
                 yield return "ReduceBlendshapeSize is need VRMBlendShapeProxy, you need to convert to VRM once.";
             }
+
+            if(Source.GetComponentsInChildren<Renderer>().All(x => !x.gameObject.activeInHierarchy))
+            {
+                yield return "No active mesh";
+            }
         }
 
         public void InitializeFrom(GameObject go)