LibWeb: Add missing JS::GCPtr wrappers in HTMLLinkElement

Author: https://github.com/mattco98
Commit: 3f22919eb5
Pull-request: https://github.com/SerenityOS/serenity/pull/17979
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/HTML/HTMLLinkElement.h

@@ -79,13 +79,13 @@ private:
         HTML::Origin origin;
         // environment
         //      An environment
-        HTML::EnvironmentSettingsObject* environment;
+        JS::GCPtr<HTML::EnvironmentSettingsObject> environment;
         // policy container
         //      A policy container
         HTML::PolicyContainer policy_container;
         // document (default null)
         //      Null or a Document
-        Web::DOM::Document* document { nullptr };
+        JS::GCPtr<Web::DOM::Document> document;
         // FIXME: on document ready (default null)
         //          Null or an algorithm accepting a Document
     };