I'm honestly not sure why you're seeing that. It's not an error we've had reported before, and that line of code wasn't changed in this latest release.
Can you let me know what version of Joomla you are using? Also, can you let me know if you ever upgraded the site from a previous major release of Joomla, like Joomla 1.5 or 2.5?
In the meantime, that message is simply a notice to developers (us) that a call is not 100% correct. You should be able to hide those messages, which are not errors in any way, by going to the Global Configuration area of Joomla and setting Error Reporting to "None".
I hope that helps,
Alex