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

Source/core/xml/XPathStep.cpp

 /*
  * Copyright (C) 2005 Frerich Raabe <raabe@kde.org>
  * Copyright (C) 2006, 2009 Apple Inc. All rights reserved.
  * 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
@@ skipping 365 matching lines @@
             RefPtrWillBeRawPtr<Node> n = contextElement->getAttributeNodeNS(nodeTest().namespaceURI(), nodeTest().data());
             // In XPath land, namespace nodes are not accessible on the attribute axis.
             if (n && n->namespaceURI() != XMLNSNames::xmlnsNamespaceURI) {
                 // Still need to check merged predicates.
                 if (nodeMatches(evaluationContext, n.get(), AttributeAxis, nodeTest()))
                     nodes.append(n.release());
             }
             return;
         }
 
-        if (!contextElement->hasAttributes())
-            return;
-
         AttributeCollection attributes = contextElement->attributes();
         AttributeCollection::const_iterator end = attributes.end();
         for (AttributeCollection::const_iterator it = attributes.begin(); it != end; ++it) {
             RefPtrWillBeRawPtr<Attr> attr = contextElement->ensureAttr(it->name());
             if (nodeMatches(evaluationContext, attr.get(), AttributeAxis, nodeTest()))
                 nodes.append(attr.release());
         }
         return;
     }
 
@@ skipping 35 matching lines @@
         nodes.markSorted(false);
         return;
     }
     }
     ASSERT_NOT_REACHED();
 }
 
 }
 
 }