lucascarder

Well, I tried adding it to all before_widget and the error message persisted.

Some variations I tried:

//register the default sidebar
register_sidebar(array(
    'name'=> TD_THEME_NAME . ' default',
    'id' => 'td-default', //the id is used by the importer
    'before_widget' => '<div id="%1$s" class="widget %2$s"><aside class="widget %2$s">',
    'after_widget' => '</aside></div>',
    'before_title' => '<div class="block-title"><span>',
    'after_title' => '</span></div>'
));

'before_widget' => '<aside id="%1$s" class="widget %2$s">',
    'after_widget' => '</aside>',

register_sidebar(array(
    'name'=>'Top right (social)',
    'id' => 'td-top-right',
    'before_widget' => '<div id="%1$s" class="widget %2$s">',
    'after_widget' => '</div>',
    'before_title' => '',
    'after_title' => '',
));

The second variation excludes the error message but the widget becomes completely blank.

Yes, that seems to be the problem. When I applied the CSS block, the space got shorter, but still there.

Any idea on how I would fix it?

Thank you