title: NSMutableRLEArray objectAtIndex:effectiveRange:: Out of bounds
body: <p>I try to assign attributes to 3 last chars of <code>newClock</code> string, which is <code>@"3:33:23"</code>.</p>
  
  <p>However I  get an error when construct <code>NSRange</code>:</p>
  
  <pre><code>NSMutableAttributedString *mas = [[NSMutableAttributedString alloc]initWithString:newClock];
  [mas addAttributes:@{NSForegroundColorAttributeName:[UIColor grayColor],
  NSFontAttributeName:[UIFont fontWithName:@"HelveticaNeue-Light" size:12]}
   range:NSMakeRange(newClock.length-3,newClock.length)];
  </code></pre>