Body of the page is blank when track outbound links is ON

GA for WP returns NULL on the_content filter on line #425 in class-frontend.php when “Track outbound links” option is turned on. I wasn’t able to detect the actual problem that causes it, but it happens during the replacements on line #431:

$text = preg_replace_callback( $anchorPattern, array( $this, 'parse_article_link' ), $text );

The actual HTML that is being broken is located here: https://gist.github.com/anonymous/0c0f044c1a352a46a369

I’d appreciate if you could look into it. Thank you!

https://wordpress.org/plugins/google-analytics-for-wordpress/