menu item for current page is missing a href tag for anonymous user
I fixed this issue by overriding menu.html.twig. You could override menu--main.html.twig instead, if you just want to target the main menu: 

menu.html.twig

&lt;li{{ item.attributes.addClass(classes) }}&gt;
  ##REPLACE THIS LINE:## {{ link(item.title, item.url) }}
  ##WITH THIS LINE:## &lt;a data-drupal-link-system-path="{{ item.url }}" title="{{ item.title }}" href="{{ item.url }}"&gt;{{ item.title }}&lt;/a&gt;
  {% if item.below %}
    {{ menus.menu_links(item.below, attributes, menu_level + 1) }}
  {% endif %}
&lt;/li&gt;


I submitted a bug report here: https://www.drupal.org/node/2695619