Merge 123377 - Crash when setting empty class name on a new element

Source/WebCore/dom/StyledElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 154 matching lines @@
     for (i = 0; i < length; ++i) {
         if (isNotHTMLSpace(characters[i]))
             break;
     }
     bool hasClass = i < length;
     if (hasClass) {
         const bool shouldFoldCase = document()->inQuirksMode();
         ensureAttributeData()->setClass(newClassString, shouldFoldCase);
         if (DOMTokenList* classList = optionalClassList())
             static_cast<ClassList*>(classList)->reset(newClassString);
-    } else
+    } else if (attributeData())
         attributeData()->clearClass();
     setNeedsStyleRecalc();
 }
 
 void StyledElement::styleAttributeChanged(const AtomicString& newStyleString, ShouldReparseStyleAttribute shouldReparse)
 {
     if (shouldReparse) {
         WTF::OrdinalNumber startLineNumber = WTF::OrdinalNumber::beforeFirst();
         if (document() && document()->scriptableDocumentParser() && !document()->isInDocumentWrite())
             startLineNumber = document()->scriptableDocumentParser()->lineNumber();
@@ skipping 160 matching lines @@
 {
     style->setProperty(propertyID, cssValuePool().createValue(value, unit));
 }
     
 void StyledElement::addPropertyToAttributeStyle(StylePropertySet* style, CSSPropertyID propertyID, const String& value)
 {
     style->setProperty(propertyID, value, false, document()->elementSheet()->contents());
 }
 
 }