I am very new with php code and I keep getting this error on my site:

OW Debug - Notice
Message: Undefined offset: 0
Line 74

I tried changing the Debug from true to false and viceversa but I doesn't work.

Line 73 and 74 say the following:
usort($this->menuItems, array(BOL_NavigationService::getInstance(), 'sortObjectListByAsc'));
return $this->menuItems[0];

Any ideas what I should change? it doesn't let me get to the admin page of the website. Thanks in advance!