Why logo image downloaded with PHP server?

When I open my blog in web browser (browser has cached most content from it and has same IP as server) I get some strange line in nginx/access.log:

MY.IP.AD.DR - - […] "GET / HTTP/1.1" 302 169 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:37.0) Gecko/20100101 Firefox/37.0"
MY.IP.AD.DR - - […] "GET /wordpress/ HTTP/1.1" 302 0 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:37.0) Gecko/20100101 Firefox/37.0"
MY.IP.AD.DR - - […] "GET /wordpress/wp-content/uploads/2013/03/logo.png HTTP/1.0" 200 6467 "-" "-"
MY.IP.AD.DR - - […] "GET /wordpress/ru/ HTTP/1.1" 200 23336 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:37.0) Gecko/20100101 Firefox/37.0"

notice line /wordpress/wp-content/uploads/2013/03/logo.png HTTP/1.0″ 200 6467 “-” “-“
it’s not browser, it’s PHP-FPM server behind Nginx server requesting image from itself…

The reason appear in file “wp-content/themes/first/inc/template-tags.php” in code

list( $logo_width ) = getimagesize( $logo_src );
 	if ( get_theme_mod( 'first_retina_logo' ) ) {
 		$logo_width = round( $logo_width / 2 );
 	}

if I comment out this lines there is no image download by PHP-FPM.

Should it be like this? Or this is bug? Or maybe I configured my server wrong?