js error saving the edits in backend

Hi, I've just installed t3 but I noticed if I try to save the edits in backend clicking on Save
I get a js error Uncaught TypeError: Cannot read property 'isValid' of undefined (index.php?option=com_templates&view=style&layout=edit&id=11:50)

http://www.awesomescreenshot.com/image/117578/c69be52f4e8404756e87a15ec717f44c

Joomla! 3.4.1 and t3 2.4.8