fix: stabilize embedded WeKnora detail page

frontend-web/src/strategy-components/components/resource-management/llmwiki/WeKnoraKnowledgeDetailPage.tsx

@@ -51,7 +51,15 @@ function collectThemePayload(): DeerFlowThemePayload {
 function postThemeToFrame(frame: HTMLIFrameElement | null) {
   if (!frame?.contentWindow) return;
   const src = frame.getAttribute("src") || "";
+  if (!src) return;
   const targetOrigin = new URL(src, window.location.href).origin;
+  try {
+    const currentUrl = frame.contentWindow.location.href;
+    if (!currentUrl || currentUrl === "about:blank") return;
+    if (new URL(currentUrl, window.location.href).origin !== targetOrigin) return;
+  } catch {
+    // Reading location throws once the iframe has reached the cross-origin backend.
+  }
   frame.contentWindow.postMessage(collectThemePayload(), targetOrigin);
 }