b/139670642: Don't filter out empty nodes named "empty_"

We use these for non-exportable things.

Change-Id: Id000b01514d953a991eee0ba70f12e0c7127b1f1

UnitySDK/Assets/TiltBrush/Scripts/Gltf/ImportGltf.cs

@@ -430,7 +430,13 @@ static IEnumerable CreateGameObjectsFromNode(
       ImportState state, Transform parent, GltfNodeBase node, GltfImportResult result,
       GltfMaterialConverter matConverter, Vector3 translationToApply) {
     if (node.Mesh == null && !node.Children.Any()) {
-      yield break;
+      if (node.name != null && node.name.StartsWith("empty_")) {
+        // explicitly-empty nodes are used to mark things like non-exportable models
+        /* fall through */
+      } else {
+        // Other empty nodes can creep in, like the SceneLight_ nodes. Don't want those.
+        yield break;
+      }
     }
 
     GameObject obj = new GameObject(node.name);