Getting strange errors

When i paste the short code to embedd the example portfolio included in the install I get a strange error that crashes my page.

Fatal error: Call to undefined method WP_Error::get_size() in /rit_sg_ssd/web_env/www_apps/sg_sites/wp-content/plugins/portfolio-gallery/Front_end/portfolio_front_end_view.php on line 764

is the error.

My site is being run on a server with multiple wordpress installs hosted on different domains im not sure if that would do it.

https://wordpress.org/plugins/portfolio-gallery/