[fix] #4740 Users Notes: headers show when no record

https://github.com/joomla/joomla-cms/issues/4740

result after patch when no record:
![screen shot 2014-10-17 at 12 26 14](https://cloud.githubusercontent.com/assets/869724/4677487/14db6c0c-55e8-11e4-9eab-df2b359f8e84.png)