Duplicate site name in title header

Hello,

I had a problem with your theme, that I did not encounter with other themes I tried (a dozen). On every page, there was a problem with the <title> header.
On the home page, I had: “<site_name> | <site_description><site_name> | <site_description>”
And on other pages (like blog post, archives, author page etc.) I had: “<page_name> | <site_name><site_name>” (if I remember correctly, but I’m not sure for this last one)

I had to go to the template-tags.php file and commment these lines to make it work “like it should” :

$title .= get_bloginfo( 'name' );
		$site_description = get_bloginfo( 'description', 'display' );

		if ( $site_description && ( is_home() || is_front_page() ) ) {
			$title = "$title $sep $site_description";
		}

This is strange, because it’s the exact same code that is registered as a “wp_title” filter on the default WordPress “twenty fourteen” theme, and I don’t have this duplicate title problem with this theme.
It seems like another “title formater” function is called when I use your theme although it shouldn’t be, that is NOT called when I use for example Twenty Fourteen.

I don’t know if the problem can be reproduced. Fyi, I work on a fresh WP installation, with only a few extensions (and _no_ SEO extensions messing with the title header), like Jetpack, Akismet, and other irrelevant ones.