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

Source/core/xml/XPathFunctions.cpp

 /*
  * Copyright (C) 2005 Frerich Raabe <raabe@kde.org>
  * Copyright (C) 2006, 2009 Apple Inc.
  * 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 584 matching lines @@
 
 Value FunLang::evaluate(EvaluationContext& context) const
 {
     String lang = arg(0)->evaluate(context).toString();
 
     const Attribute* languageAttribute = 0;
     Node* node = context.node.get();
     while (node) {
         if (node->isElementNode()) {
             Element* element = toElement(node);
-            if (element->hasAttributes())
-                languageAttribute = element->attributes().find(XMLNames::langAttr);
+            languageAttribute = element->attributes().find(XMLNames::langAttr);
         }
         if (languageAttribute)
             break;
         node = node->parentNode();
     }
 
     if (!languageAttribute)
         return false;
 
     String langValue = languageAttribute->value();
@@ skipping 127 matching lines @@
         return 0;
 
     Function* function = functionRec->factoryFn();
     function->setArguments(args);
     function->setName(name);
     return function;
 }
 
 }
 }