Updated WordPress – now I have a curious unbracketed CSS element showing up

If you see image of site (still under construction) here:

Where the horizontal nav menu is located, there is a rogue ‘class=””>’ now inserted after I upgraded WordPress.

The relevant source code element shows as follows

<div id="menu" class="dropdown">
      <ul id="nav"><li class="home"><a href="https://ebbsfleetunited.co.uk/z2012" rel="nofollow"><img src="https://ebbsfleetunited.co.uk/z2012/wp-content/themes/fleetred/images/men_icon_home.png" alt="" width="16" height="14"></a></li>class=""><li id="menu-item-1860" class="menu-item menu-item-type-taxonomy menu-item-object-category menu-item-1860"><a href="https://ebbsfleetunited.co.uk/z2012/?cat=7">THE CLUB</a></li>

I’ve tried poring through various pages to see if I can see where this might be occurring but, being a total code amateur, no luck. Help!