clear double iframe more safe

Html/apps/templates/desktop.html

@@ -169,20 +169,16 @@
         });
 
     
-
+    let lastIframe = null;
     function OpenIframe(){
             // 在成功获取 session 后创建并插入 iframe
             const iframe = document.createElement('iframe');
             const div=document.getElementById('vscodeWeb')
-
-            const iframes = document.getElementsByTagName('iframe');
-            
-            // 删除除了第一个 iframe 外的其他所有 iframe
-            for (let i = 1; i < iframes.length; i++) {
-                iframes[i].remove();
+            if (lastIframe){
+                lastIframe.remove();
             }
     
-
+            lastIframe = iframe;
 
             const sessionInfo = data
             iframe.src = '{{vscode_web_url}}/?workspace={{workspace_path}}&folder={{workspace_path}}';