LibWeb: Add missing visit Node::m_pseudo_element_generator

Userland/Libraries/LibWeb/Layout/Node.cpp

@@ -51,6 +51,7 @@ void Node::visit_edges(Cell::Visitor& visitor)
     Base::visit_edges(visitor);
     visitor.visit(m_dom_node);
     visitor.visit(m_paintable);
+    visitor.visit(m_pseudo_element_generator);
     visitor.visit(m_browsing_context);
     TreeNode::visit_edges(visitor);
 }