When previewing Largo or a child theme using the Customizer or the "preview theme" option, Class '' not found

[benlk]

Fatal error: Uncaught Error: Class '' not found in /wp-content/themes/largo/homepages/homepage.php:79
Stack trace:
#0 /wp-content/themes/largo/home.php(35): largo_render_homepage_layout('')
#1 /wp-includes/template-loader.php(78): include('/...')
#2 /wp-blog-header.php(19): require_once('/...')
#3 /index.php(17): require('/...')
#4 ~/.composer/vendor/laravel/valet/server.php(158): require('/...')
#5 {main} thrown in /Users/blk/sites/workdayminn/wp-content/themes/largo/homepages/homepage.php on line 79

https://github.com/INN/largo/blob/0b03cb938061f9f2c64c9dee24b8be1e46356b26/homepages/homepage.php#L75-L81

The template to be loaded comes from largo_get_active_homepage_layout();

https://github.com/INN/largo/blob/0b03cb938061f9f2c64c9dee24b8be1e46356b26/home.php#L23-L35

Which comes from https://github.com/INN/largo/blob/512da701664b329f2f92244bbe54880a6e146431/homepages/homepage.php#L86-L88

of_get_option() there should be returning HomepageBlog if home_template doesn't have a defined value in the options framework options, but somehow it's returning an empty string. It returns 'HomepageBlog' dozens of times, save for during the final call that causes the fatal error.

[benlk]

This is something to test for once we've switched to the Customizer framework, as part of #1438. This bug in the Options Framework itself doesn't need to be addressed, since we'll be moving off of that.