screwed up upgrade of BP Daily

Hello,

Just did something boneheaded. I'm working on customizing BP Daily and tried to upgrade to the latest version. Not sure what I screwed up, but now I get this error message when trying to activate the theme.

Fatal error: Call to undefined function register_nav_menus() in /home5/threeshe/public_html/threesheetsnw/wp-content/themes/bp-daily/library/functions/custom-functions.php on line 21

I've tried removing and reinstalling the theme entirely, but it still shows this message. The site is just a development site, so I'm not freaking out. Just trying to figure out how to get back to work on the theme.

Thanks