Add Actor.HasScene and Script.HasScene

Useful in managed code to check the existence of the scene in hot paths
by avoiding expensive marshalling of the Scene object.

Source/Engine/Level/Actor.h

@@ -382,6 +382,15 @@ public:
         return _isActiveInHierarchy != 0;
     }
 
+    /// <summary>
+    /// Gets value indicating if actor is in a scene.
+    /// </summary>
+    API_PROPERTY(Attributes="HideInEditor, NoSerialize")
+    FORCE_INLINE bool HasScene() const
+    {
+        return _scene != nullptr;
+    }
+
     /// <summary>
     /// Returns true if object is fully static on the scene, otherwise false.
     /// </summary>