title: componentsSeparatedByString return 1 object when string is empty
body: <p>I convert string into array by componentsSeparatedByString. It return array perfect. but when string is empty return 1 object.</p>
  
  <p>why this happen ?</p>
  
  <pre><code>NSMutableArray *imagesList=[[[productDetail objectForKey:@"productImage"] componentsSeparatedByString:@","]mutableCopy];
  </code></pre>