I just try this plugin it from localhost (home computer), is it a cause make that undefined issue ?
Since when is it happening? after i install plugin.
Have you changed any configuration regarding result URL? no
Is it happening on custom post types or regular posts or something else? regular post
Is it happening on every result, or only some of them? every result
Do you have a working url where I can check this? i try from my localhost before i set on real live domain.
Are you using any kind of filter function on the results? no