<?php if ( get_header_image() ) : ?>
<div id="site-header">
<a href="<?php echo esc_url( home_url( '/' ) ); ?>" rel="home">
- <img src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="">
+ <img src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>">
</a>
</div>
<?php endif; ?>