LibWeb: Add a missing visit in HTMLFormElement

Author: https://github.com/mattco98
Commit: 4701c4bb01
Pull-request: https://github.com/SerenityOS/serenity/pull/23861
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/HTML/HTMLFormElement.cpp

@@ -61,6 +61,7 @@ void HTMLFormElement::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_elements);
     for (auto& element : m_associated_elements)
         visitor.visit(element);
+    visitor.visit(m_planned_navigation);
 }
 
 // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#implicit-submission