title: NSMutableAttributedString check nil value
body: <p>I created a <code>NSMutableAttributedString</code> and I'm appending the value dynamically. I need to check if this string is <code>nil</code> or not. I manually assigned <code>nil</code> but still the condition below fails. Is there any way to check this?</p>
  
  <pre><code> attribStr = [[NSMutableAttributedString alloc] init];
   attribStr = nil;
   if([attribStr isEqualToAttributedString:nil]) { // doesn't execute}
  </code></pre>