It is because of the var_dump, because it pollutes the json response, that the divi filter grid tries to parse – that of course will break, that’s expected when you change the output, but it’s not related to the search.
I’m afraid there it’t not yet documented, but it’s a simple boolean value of true or false. When true, it will signal Ajax Search Pro to capture and cancel the current query and replace the results from it’s own query results. That’s all it does 🙂
/**
* When true, Ajax Search Pro will capture the $wp_query (WP_Query) in the following way:
* -> on "posts_request" hook it checks if $wp_query->query_args['asp_override'] === true
* -> if true, cancels the current query by setting the request $request = ''
* -> on "posts_results" hook checks again, and overrides the posts returned with the results from it's own query
* This means that the original query is cancelled, then the results are swapped.
**/
$query_args['asp_override'] = true;