LibWeb: Avoid potential infinite recursion in Document::update_layout

Author: https://github.com/shannonbooth
Commit: https://github.com/LadybirdBrowser/ladybird/commit/aa585c4182b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2081

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -1144,7 +1144,7 @@ void Document::update_layout()
 
     // NOTE: If our parent document needs a relayout, we must do that *first*.
     //       This is necessary as the parent layout may cause our viewport to change.
-    if (navigable->container())
+    if (navigable->container() && &navigable->container()->document() != this)
         navigable->container()->document().update_layout();
 
     update_style();