fix a bug that sometime duplicate stage cameras

Author: xiaoguzhu

Assets/Scripts/Utils/Html/HtmlPageContext.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using TMPro;
 using UnityEngine;
 
 namespace FairyGUI.Utils
@@ -14,15 +15,25 @@ public class HtmlPageContext : IHtmlPageContext
         Stack<IHtmlObject> _selectPool;
         Stack<IHtmlObject> _linkPool;
 
-        public static HtmlPageContext inst = new HtmlPageContext();
+        static HtmlPageContext _inst;
+
+        public static HtmlPageContext inst
+        {
+            get
+            {
+                if (_inst == null)
+                    _inst = new HtmlPageContext();
+                return _inst;
+            }
+        }
 
         static Transform _poolManager;
 
 #if UNITY_2019_3_OR_NEWER
         [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
         static void InitializeOnLoad()
         {
-            inst = new HtmlPageContext();
+            _inst = null;
             _poolManager = null;
         }
 #endif