Debug notices in front page

Homepage loading logs in the frontend, debug mode isn't enabled, still showing the following notices:

Notice: Trying to get property of non-object in /home/xxx/public_html/wp-includes/nav-menu.php on line 780

Notice: Trying to get property of non-object in /home/xxxx/public_html/wp-includes/nav-menu.php on line 780

Notice: Trying to get property of non-object in /home/xxxx/public_html/wp-includes/nav-menu.php on line 784

https://www.sugarsync.com/pf/D646892_07204924_0909619

Please advise what could be causing, and what needs to be done to fix this.