Handle user selecting an object from a scene (#3)

Author: Unity-Harry

AssetDependencyGraph/Editor/AssetDependencyGraph.cs

@@ -105,11 +105,12 @@ public void OnDisable()
     private void ExplodeAsset()
     {
         Object obj = Selection.activeObject;
-        if (!obj)
-            return;
-
         string assetPath = AssetDatabase.GetAssetPath(obj);
 
+        // assetPath will be empty is obj is null or isn't an asset (a scene object)
+        if (obj == null || string.IsNullOrEmpty(assetPath))
+            return;
+
         Group      groupNode      = new Group {title = obj.name};
         Object     mainObject     = AssetDatabase.LoadMainAssetAtPath(assetPath);