Changed URL format and site disappeared

So I just installed a new copy of WP in a folder at https://www.patiastephens.com/test. (I already have a WP install in the main directory.) I’m hosted on GoDaddy.

Everything seemed to be working fine until I was adjusting dashboard settings for the new site. I changed the default URL format, saved, and ever since, all I get is a 500 Internal server error when trying to access the site.

What the heck?