Make Element::attributes() less error-prone and simplify call sites

Source/core/xml/XPathNodeSet.cpp

 /*
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 216 matching lines @@
     sortedNodes.reserveInitialCapacity(nodeCount);
 
     for (Node* n = findRootNode(m_nodes.first().get()); n; n = NodeTraversal::next(*n)) {
         if (nodes.contains(n))
             sortedNodes.append(n);
 
         if (!containsAttributeNodes || !n->isElementNode())
             continue;
 
         Element* element = toElement(n);
-        if (!element->hasAttributes())
-            continue;
-
         AttributeCollection attributes = element->attributes();
         AttributeCollection::const_iterator end = attributes.end();
         for (AttributeCollection::const_iterator it = attributes.begin(); it != end; ++it) {
             RefPtrWillBeRawPtr<Attr> attr = element->attrIfExists(it->name());
             if (attr && nodes.contains(attr.get()))
                 sortedNodes.append(attr);
         }
     }
 
     ASSERT(sortedNodes.size() == nodeCount);
@@ skipping 28 matching lines @@
 Node* NodeSet::anyNode() const
 {
     if (isEmpty())
         return 0;
 
     return m_nodes.at(0).get();
 }
 
 }
 }