Fix an MQ parsing related crash

Source/core/css/CSSParserValues.h

 /*
  * Copyright (C) 2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008, 2009, 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 176 matching lines @@
     CSSParserValue* previous()
     {
         if (!m_current)
             return 0;
         --m_current;
         return current();
     }
 
     CSSParserValue* valueAt(unsigned i) { return i < m_values.size() ? &m_values[i] : 0; }
 
-    void clear() { m_values.clear(); }
+    void clear() { m_values.clear(); m_current = 0;}
 
 private:
     unsigned m_current;
     Vector<CSSParserValue, 4> m_values;
 };
 
 struct CSSParserFunction {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     CSSParserString name;
@@ skipping 72 matching lines @@
 inline void CSSParserValue::setFromValueList(PassOwnPtr<CSSParserValueList> valueList)
 {
     id = CSSValueInvalid;
     this->valueList = valueList.leakPtr();
     unit = ValueList;
 }
 
 }
 
 #endif