nathanjrb Hi Nathan,
Try this solution - to allow upload SVG file through WordPress Media Uploader:
https://css-tricks.com/snippets/wordpress/allow-svg-through-wordpress-media-uploader/
If it won't work, please open wp-content/themes/portfolio/header.php file and replace the line:
<img src="<?php echo get_theme_mod('portfolio_logo', ''); ?>" alt="<?php bloginfo( 'name' ); ?>" />
with:
<img src="path_to_your.svg" alt="<?php bloginfo( 'name' ); ?>" />
You can do it via child theme, otherwise you'll have to remember about this modification during future theme updates.
Cheers
Joshua