BidiResolver should not try to reverse runs when the run count is zero

Source/core/platform/text/BidiResolver.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008 Apple Inc.  All right 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 556 matching lines @@
         m_emptyRun = false;
         m_sor = m_current;
         m_eor = Iterator();
         while (m_current != end && !m_current.atEnd()) {
             m_eor = m_current;
             increment();
         }
         m_direction = override == VisualLeftToRightOverride ? LeftToRight : RightToLeft;
         appendRun();
         m_runs.setLogicallyLastRun(m_runs.lastRun());
-        if (override == VisualRightToLeftOverride)
+        if (override == VisualRightToLeftOverride && m_runs.runCount())
             m_runs.reverseRuns(0, m_runs.runCount() - 1);
         return;
     }
 
     m_emptyRun = true;
 
     m_eor = Iterator();
 
     m_last = m_current;
     bool lastParagraphEnded = false;
@@ skipping 363 matching lines @@
     }
 
     m_runs.setLogicallyLastRun(m_runs.lastRun());
     reorderRunsFromLevels();
     endOfLine = Iterator();
 }
 
 } // namespace WebCore
 
 #endif // BidiResolver_h