WP_Error could not be converted to string in

After update I got this error:

Fatal error: Uncaught Error: Object of class WP_Error could not be converted to string in /var/sites/v/villamarts.co.uk/public_html/wp-content/plugins/woocommerce/includes/walkers/class-wc-product-cat-list-walker.php:105

The line 105, is: 

$output .= ‘”>tree_type ) . ‘”>’ . apply_filters( ‘list_product_cats’, $cat->name, $cat ) . ‘‘;

And here is the whole function:

public function start_el( &$output, $cat, $depth = 0, $args = array(), $current_object_id = 0 ) {
		$cat_id = intval( $cat->term_id );

		$output .= '<li class="cat-item cat-item-' . $cat_id;

		if ( $args['current_category'] === $cat_id ) {
			$output .= ' current-cat';
		}

		if ( $args['has_children'] && $args['hierarchical'] && ( empty( $args['max_depth'] ) || $args['max_depth'] > $depth + 1 ) ) {
			$output .= ' cat-parent';
		}

		if ( $args['current_category_ancestors'] && $args['current_category'] && in_array( $cat_id, $args['current_category_ancestors'], true ) ) {
			$output .= ' current-cat-parent';
		}

		$output .= '"><a href="' . get_term_link( $cat_id, $this->tree_type ) . '">' . apply_filters( 'list_product_cats', $cat->name, $cat ) . '</a>';

		if ( $args['show_count'] ) {
			$output .= ' <span class="count">(' . $cat->count . ')</span>';
		}
	}

Please someone could help. me on this?

The page I need help with: [log in to see the link]