I'm getting a Fatal PHP error in my logs. I've reached out

I'm getting a Fatal PHP error in my logs. I've reached out to the theme developer who said they haven't seen this on any installation. Can you help me figure out what's going on? This is the error:

[Fri Jun 19 03:12:35 2015] [error] [client 162.216.16.33] PHP Fatal error: Call to a member function webnus_blog_template() on a non-object in /MYSITE/wp-content/themes/florida-wp/index.php on line 23

This is line 23 of that file:

$blogType = $webnus_options->webnus_blog_template();