style: Use option invoke

Author: jcs090218

Assets/JCSUnity/Scripts/Util/JCS_Util.cs

@@ -1147,17 +1147,15 @@ public static void WithActiveScene(Scene scene, System.Action action)
             // If the same scene, just execute and leave.
             if (oldScene == scene)
             {
-                if (action != null)
-                    action.Invoke();
+                action?.Invoke();
 
                 return;
             }
 
             // Switch to new scene.
             SceneManager.SetActiveScene(scene);
 
-            if (action != null)
-                action.Invoke();
+            action?.Invoke();
 
             // Revert back to old scene.
             SceneManager.SetActiveScene(oldScene);