title: NSString returning NULL while doing NSUTF8StringEncoding
body: <p>Following is my code </p>
  
  <pre><code>NSString *res = [valueArray valueForKey:@"key"];
  NSData *newdata=[res dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];
  res=[[NSString alloc] initWithData:newdata encoding:NSNonLossyASCIIStringEncoding];
  nameTxt.text = [NSString stringWithFormat:@"%@",res]; // Assigning to textfield
  </code></pre>
  
  <p>this works properly.
  But sometimes it returns NULL data, mostly it happens when string contents large data.</p>
  
  <p>Anyone have idea why this is happening?</p>